Researcher in atomic physics at the Department of Physics at Stockholm University

Telephone: +46-8-5537-8634

Mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Research interest:

 Charge transfer, energy flow, and bond formation processes in interactions involving atoms, molecules, and clusters.

 Stabilities and reactivities of multiply charged molecules and weakly bound negatively charged molecules.

Radiation damage of biomolecules in vacuum and in nanosolvents.

 

My recent publications:

  1. Fredrik Linden, Henrik Cederquist and Henning Zettergren.
    Interaction and charge transfer between dielectric spheres: Exact and approximate analytical solutions. The Journal of Chemical Physics 145(19):, 2016.
    URL, DOI BibTeX

    @article{:/content/aip/journal/jcp/145/19/10.1063/1.4967701,
    	author = "Linden, Fredrik and Cederquist, Henrik and Zettergren, Henning",
    	title = "Interaction and charge transfer between dielectric spheres: Exact and approximate analytical solutions",
    	journal = "The Journal of Chemical Physics",
    	year = 2016,
    	volume = 145,
    	number = 19,
    	eid = 194307,
    	pages = "",
    	url = "http://scitation.aip.org/content/aip/journal/jcp/145/19/10.1063/1.4967701",
    	doi = "http://dx.doi.org/10.1063/1.4967701"
    }
    
  2. S E Huber, M Gatchell, H Zettergren and A Mauracher.
    A precedent of van-der-Waals interactions outmatching Coulomb explosion. Carbon 109():843 - 850, 2016.
    URL, DOI BibTeX

    @article{Huber2016843,
    	title = "A precedent of van-der-Waals interactions outmatching Coulomb explosion",
    	journal = "Carbon",
    	volume = 109,
    	number = "",
    	pages = "843 - 850",
    	year = 2016,
    	note = "",
    	issn = "0008-6223",
    	doi = "http://dx.doi.org/10.1016/j.carbon.2016.08.056",
    	url = "http://www.sciencedirect.com/science/article/pii/S0008622316307114",
    	author = "S.E. Huber and M. Gatchell and H. Zettergren and A. Mauracher"
    }
    
  3. K C Chartkunchand, M Kamiıfmmode \acuten\else ń\fiska, E K Anderson, M K Kristiansson, G Eklund, O M Hole, R F Nascimento, M Blom, M Björkhage, A Källberg, P Löfgren, P Reinhed, S Rosén, A Simonsson, R D Thomas, S Mannervik, V T Davis, P A Neill, J S Thompson, D Hanstorp, H Zettergren, H Cederquist and H T Schmidt.
    Radiative lifetimes of the bound excited states of Pt^-. Phys. Rev. A 94:032501, September 2016.
    URL, DOI BibTeX

    @article{PhysRevA.94.032501,
    	title = "Radiative lifetimes of the bound excited states of Pt^-",
    	author = {Chartkunchand, K. C. and Kami\ifmmode \acute{n}\else \'{n}\fi{}ska, M. and Anderson, E. K. and Kristiansson, M. K. and Eklund, G. and Hole, O. M. and Nascimento, R. F. and Blom, M. and Bj\"orkhage, M. and K\"allberg, A. and L\"ofgren, P. and Reinhed, P. and Ros\'en, S. and Simonsson, A. and Thomas, R. D. and Mannervik, S. and Davis, V. T. and Neill, P. A. and Thompson, J. S. and Hanstorp, D. and Zettergren, H. and Cederquist, H. and Schmidt, H. T.},
    	journal = "Phys. Rev. A",
    	volume = 94,
    	issue = 3,
    	pages = 032501,
    	numpages = 6,
    	year = 2016,
    	month = "Sep",
    	publisher = "American Physical Society",
    	doi = "10.1103/PhysRevA.94.032501",
    	url = "http://link.aps.org/doi/10.1103/PhysRevA.94.032501"
    }
    
  4. Kostiantyn Kulyk, Henning Zettergren, Michael Gatchell, John D Alexander, Mykola Borysenko, Borys Palianytsia, Mats Larsson and Tetiana Kulik.
    Dimethylsilanone Generation from Pyrolysis of Polysiloxanes Filled with Nanosized Silica and Ceria/Silica. ChemPlusChem 81(9):1003–1013, 2016.
    URL, DOI BibTeX

    @article{CPLU:CPLU201600229,
    	author = "Kulyk, Kostiantyn and Zettergren, Henning and Gatchell, Michael and Alexander, John D. and Borysenko, Mykola and Palianytsia, Borys and Larsson, Mats and Kulik, Tetiana",
    	title = "Dimethylsilanone Generation from Pyrolysis of Polysiloxanes Filled with Nanosized Silica and Ceria/Silica",
    	journal = "ChemPlusChem",
    	volume = 81,
    	number = 9,
    	issn = "2192-6506",
    	url = "http://dx.doi.org/10.1002/cplu.201600229",
    	doi = "10.1002/cplu.201600229",
    	pages = "1003--1013",
    	keywords = "kinetics, mass spectrometry, polysiloxanes, pyrolysis, silica",
    	year = 2016
    }
    
  5. Kostiantyn Kulyk, Henning Zettergren, Michael Gatchell, John D Alexander, Mykola Borysenko, Borys Palianytsia, Mats Larsson and Tetiana Kulik.
    Inside Cover: Dimethylsilanone Generation from Pyrolysis of Polysiloxanes Filled with Nanosized Silica and Ceria/Silica (ChemPlusChem 9/2016). ChemPlusChem 81(9):902–902, 2016.
    URL, DOI BibTeX

    @article{CPLU:CPLU201600411,
    	author = "Kulyk, Kostiantyn and Zettergren, Henning and Gatchell, Michael and Alexander, John D. and Borysenko, Mykola and Palianytsia, Borys and Larsson, Mats and Kulik, Tetiana",
    	title = "Inside Cover: Dimethylsilanone Generation from Pyrolysis of Polysiloxanes Filled with Nanosized Silica and Ceria/Silica (ChemPlusChem 9/2016)",
    	journal = "ChemPlusChem",
    	volume = 81,
    	number = 9,
    	issn = "2192-6506",
    	url = "http://dx.doi.org/10.1002/cplu.201600411",
    	doi = "10.1002/cplu.201600411",
    	pages = "902--902",
    	keywords = "kinetics, mass spectrometry, polysiloxanes, pyrolysis, silica",
    	year = 2016
    }
    
  6. Michael Gatchell and Henning Zettergren.
    Knockout driven reactions in complex molecules and their clusters. Journal of Physics B: Atomic, Molecular and Optical Physics 49(16):162001, 2016.
    URL BibTeX

    @article{0953-4075-49-16-162001,
    	author = "Michael Gatchell and Henning Zettergren",
    	title = "Knockout driven reactions in complex molecules and their clusters",
    	journal = "Journal of Physics B: Atomic, Molecular and Optical Physics",
    	volume = 49,
    	number = 16,
    	pages = 162001,
    	url = "http://stacks.iop.org/0953-4075/49/i=16/a=162001",
    	year = 2016
    }
    
  7. Michael Wolf, Linda Giacomozzi, Michael Gatchell, Nathalie Ruette, Mark H Stockett, Henning T Schmidt, Henrik Cederquist and Henning Zettergren.
    Hydrogenated pyrene: Statistical single-carbon loss below the knockout threshold. EUROPEAN PHYSICAL JOURNAL D 70(4), 2016.
    DOI BibTeX

    @article{ ISI:000375296200002,
    	author = "Wolf, Michael and Giacomozzi, Linda and Gatchell, Michael and de Ruette, Nathalie and Stockett, Mark H. and Schmidt, Henning T. and Cederquist, Henrik and Zettergren, Henning",
    	title = "{Hydrogenated pyrene: Statistical single-carbon loss below the knockout threshold}",
    	journal = "{EUROPEAN PHYSICAL JOURNAL D}",
    	year = "{2016}",
    	volume = "{70}",
    	number = "{4}",
    	month = "{APR 14}",
    	doi = "{10.1140/epjd/e2016-60735-3}",
    	article-number = "{85}",
    	issn = "{1434-6060}",
    	eissn = "{1434-6079}",
    	researcherid-numbers = "{Schmidt, Henning/H-6277-2016}",
    	unique-id = "{ISI:000375296200002}"
    }
    
  8. M H Stockett, M Gatchell, N Ruette, L Giacomozzi, T Chen, P Rousseau, S Maclot, J -Y Chesnel, L Adoui, B A Huber, U Bērziņš, H T Schmidt, H Zettergren and H Cederquist.
    Isomer effects in fragmentation of Polycyclic Aromatic Hydrocarbons. International Journal of Mass Spectrometry 392():58, 2015.
    URL, DOI BibTeX

    @article{Stockett2015,
    	title = "Isomer effects in fragmentation of Polycyclic Aromatic Hydrocarbons",
    	journal = "International Journal of Mass Spectrometry",
    	volume = 392,
    	number = "",
    	pages = 58,
    	year = 2015,
    	note = "",
    	issn = "1387-3806",
    	doi = "http://dx.doi.org/10.1016/j.ijms.2015.09.005",
    	url = "http://www.sciencedirect.com/science/article/pii/S1387380615003140",
    	author = "M.H. Stockett and M. Gatchell and N. de Ruette and L. Giacomozzi and T. Chen and P. Rousseau and S. Maclot and J.-Y. Chesnel and L. Adoui and B.A. Huber and U. Bērziņš and H.T. Schmidt and H. Zettergren and H. Cederquist",
    	keywords = "Non-statistical fragmentation"
    }
    
  9. M H Stockett, M Gatchell, T Chen, N Ruette, L Giacomozzi, M Wolf, H T Schmidt, H Zettergren and H Cederquist.
    Threshold Energies for Single-Carbon Knockout from Polycyclic Aromatic Hydrocarbons. The Journal of Physical Chemistry Letters 6(22):4504-4509, 2015.
    URL, DOI BibTeX

    @article{doi:10.1021/acs.jpclett.5b02080,
    	author = "M. H. Stockett and M. Gatchell and T. Chen and N. de Ruette and L. Giacomozzi and M. Wolf and H. T. Schmidt and H. Zettergren and H. Cederquist",
    	title = "Threshold Energies for Single-Carbon Knockout from Polycyclic Aromatic Hydrocarbons",
    	journal = "The Journal of Physical Chemistry Letters",
    	volume = 6,
    	number = 22,
    	pages = "4504-4509",
    	year = 2015,
    	doi = "10.1021/acs.jpclett.5b02080",
    	note = "PMID: 26523738",
    	url = "http://dx.doi.org/10.1021/acs.jpclett.5b02080"
    }
    
  10. M Gatchell, M H Stockett, N Ruette, T Chen, L Giacomozzi, R F Nascimento, M Wolf, E K Anderson, R Delaunay, V Vizcaino, P Rousseau, L Adoui, B A Huber, H T Schmidt, H Zettergren and H Cederquist.
    Failure of hydrogenation in protecting polycyclic aromatic hydrocarbons from fragmentation. Phys. Rev. A 92:050702(R), 2015.
    URL, DOI BibTeX

    @article{PhysRevA.92.050702,
    	title = "Failure of hydrogenation in protecting polycyclic aromatic hydrocarbons from fragmentation",
    	author = "Gatchell, M. and Stockett, M. H. and de Ruette, N. and Chen, T. and Giacomozzi, L. and Nascimento, R. F. and Wolf, M. and Anderson, E. K. and Delaunay, R. and Vizcaino, V. and Rousseau, P. and Adoui, L. and Huber, B. A. and Schmidt, H. T. and Zettergren, H. and Cederquist, H.",
    	journal = "Phys. Rev. A",
    	volume = 92,
    	issue = 5,
    	pages = "050702(R)",
    	numpages = 5,
    	year = 2015,
    	publisher = "American Physical Society",
    	doi = "10.1103/PhysRevA.92.050702",
    	url = "http://link.aps.org/doi/10.1103/PhysRevA.92.050702"
    }
    
  11. Kostiantyn Kulyk, Oleksii Rebrov, Mark H Stockett, John D Alexander, Henning Zettergren, Henning T Schmidt, Richard D Thomas, Henrik Cederquist and Mats Larsson.
    High-energy collisions of protonated enantiopure amino acids with a chiral target gas. International Journal of Mass Spectrometry 388():59, 2015.
    URL, DOI BibTeX

    @article{Kulyk201559,
    	title = "High-energy collisions of protonated enantiopure amino acids with a chiral target gas",
    	journal = "International Journal of Mass Spectrometry",
    	volume = 388,
    	number = "",
    	pages = 59,
    	year = 2015,
    	note = "",
    	issn = "1387-3806",
    	doi = "http://dx.doi.org/10.1016/j.ijms.2015.08.010",
    	url = "http://www.sciencedirect.com/science/article/pii/S1387380615002614",
    	author = "Kostiantyn Kulyk and Oleksii Rebrov and Mark H. Stockett and John D. Alexander and Henning Zettergren and Henning T. Schmidt and Richard D. Thomas and Henrik Cederquist and Mats Larsson",
    	keywords = "2-Butanol"
    }
    
  12. Rudy Delaunay, Michael Gatchell, Patrick Rousseau, Alicja Domaracka, Sylvain Maclot, Yang Wang, Mark H Stockett, Tao Chen, Lamri Adoui, Manuel Alcami, Fernando Martin, Henning Zettergren, Henrik Cederquist and Bernd A Huber.
    Molecular Growth Inside of Polycyclic Aromatic Hydrocarbon Clusters Induced by Ion Collisions. JOURNAL OF PHYSICAL CHEMISTRY LETTERS 6(9):1536-1542, 2015.
    DOI BibTeX

    @article{ ISI:000355014900006,
    	author = "Delaunay, Rudy and Gatchell, Michael and Rousseau, Patrick and Domaracka, Alicja and Maclot, Sylvain and Wang, Yang and Stockett, Mark H. and Chen, Tao and Adoui, Lamri and Alcami, Manuel and Martin, Fernando and Zettergren, Henning and Cederquist, Henrik and Huber, Bernd A.",
    	title = "{Molecular Growth Inside of Polycyclic Aromatic Hydrocarbon Clusters Induced by Ion Collisions}",
    	journal = "{JOURNAL OF PHYSICAL CHEMISTRY LETTERS}",
    	year = "{2015}",
    	volume = "{6}",
    	number = "{9}",
    	pages = "{1536-1542}",
    	month = "{MAY 7}",
    	doi = "{10.1021/acs.jpclett.5b00405}",
    	issn = "{1948-7185}",
    	researcherid-numbers = "{Wang, Yang/A-2602-2015 Gatchell, Michael/O-2335-2015 Maclot, Sylvain /O-3225-2015}",
    	orcid-numbers = "{Wang, Yang/0000-0003-2540-2199 Maclot, Sylvain /0000-0001-5587-7182}",
    	unique-id = "{ISI:000355014900006}"
    }
    
  13. T Chen, M Gatchell, M H Stockett, R Delaunay, A Domaracka, E R Micelotta, A G G M Tielens, P Rousseau, L Adoui, B A Huber, H T Schmidt, H Cederquist and H Zettergren.
    Formation of H2 from internally heated polycyclic aromatic hydrocarbons: Excitation energy dependence. The Journal of Chemical Physics 142:144305, 2015.
    URL, DOI BibTeX

    @article{:/content/aip/journal/jcp/142/14/10.1063/1.4917021,
    	author = "Chen, T. and Gatchell, M. and Stockett, M. H. and Delaunay, R. and Domaracka, A. and Micelotta, E. R. and Tielens, A. G. G. M. and Rousseau, P. and Adoui, L. and Huber, B. A. and Schmidt, H. T. and Cederquist, H. and Zettergren, H.",
    	title = "Formation of H2 from internally heated polycyclic aromatic hydrocarbons: Excitation energy dependence",
    	journal = "The Journal of Chemical Physics",
    	year = 2015,
    	volume = 142,
    	pages = 144305,
    	url = "http://scitation.aip.org/content/aip/journal/jcp/142/14/10.1063/1.4917021",
    	doi = "http://dx.doi.org/10.1063/1.4917021"
    }
    
  14. Henning Zettergren.
    Ions interacting with complex molecular systems: The effect of a surrounding environment. Journal of Physics: Conference Series 629(1):012003, 2015.
    URL BibTeX

    @article{1742-6596-629-1-012003,
    	author = "Henning Zettergren",
    	title = "Ions interacting with complex molecular systems: The effect of a surrounding environment",
    	journal = "Journal of Physics: Conference Series",
    	volume = 629,
    	number = 1,
    	pages = 012003,
    	url = "http://stacks.iop.org/1742-6596/629/i=1/a=012003",
    	year = 2015,
    	abstract = "This paper highlight results from studies of keV-ion impact on complex molecules and molecular clusters, which have been carried out at the ARIBE facility in Caen (France) during the last decade. Studies of fullerenes, Polycyclic Aromatic Hydrocarbons (PAHs), and biomolecules are reviewed with focus on the effect of a surrounding environment when ions interact with weakly bound clusters of theses species. One common result is that charge and energy are rapidly shared between the individual molecules in the clusters, in contrast to e.g. weakly bound atomic clusters where the charge stay localized to a few atoms from which the electrons are removed during the collisions. Another important finding is that ion collisions may induce reactions within clusters such as e.g. proton transfer and different types of molecular growth processes. In the latter case, these processes may be driven by prompt non-statistical atom knockouts in billiard-ball like atom-atom collisions favouring highly reactive fragments. In contrast, statistical fragmentation in general yields different and less reactive fragments."
    }
    
  15. M H Stockett, M Gatchell, J D Alexander, U Berzins, T Chen, K Farid, A Johansson, K Kulyk, P Rousseau, K Stochkel, L Adoui, P Hvelplund, B A Huber, H T Schmidt, H Zettergren and H Cederquist.
    Fragmentation of anthracene C14H10, acridine C13H9N and phenazine C12H8N2 ions in collisions with atoms. Phys. Chem. Chem. Phys. 16:21980, 2014.
    URL, DOI BibTeX

    @article{C4CP03293D,
    	author = "Stockett, M. H. and Gatchell, M. and Alexander, J. D. and Berzins, U. and Chen, T. and Farid, K. and Johansson, A. and Kulyk, K. and Rousseau, P. and Stochkel, K. and Adoui, L. and Hvelplund, P. and Huber, B. A. and Schmidt, H. T. and Zettergren, H. and Cederquist, H.",
    	doi = "10.1039/C4CP03293D",
    	journal = "Phys. Chem. Chem. Phys.",
    	volume = 16,
    	issue = 40,
    	pages = 21980,
    	publisher = "The Royal Society of Chemistry",
    	title = "Fragmentation of anthracene C14H10{,} acridine C13H9N and phenazine C12H8N2 ions in collisions with atoms",
    	url = "http://dx.doi.org/10.1039/C4CP03293D",
    	year = 2014,
    	bdsk-url-1 = "http://dx.doi.org/10.1039/C4CP03293D"
    }
    
  16. Humberto Silva, Javier Oller, Michael Gatchell, Mark H Stockett, Paul-Antoine Hervieux, Lamri Adoui, Manuel Alcamí, Bernd A Huber, Fernando Martín, Henrik Cederquist, Henning Zettergren, Patrick Rousseau and Sergio Díaz-Tendero.
    Multiple electron capture, excitation, and fragmentation in C6+ + C60 collisions. Phys. Rev. A 90:032701, 2014.
    URL, DOI BibTeX

    @article{PhysRevA.90.032701,
    	title = "Multiple electron capture, excitation, and fragmentation in C6+ + C60 collisions",
    	author = "da Silva, Humberto and Oller, Javier and Gatchell, Michael and Stockett, Mark H. and Hervieux, Paul-Antoine and Adoui, Lamri and Alcam\'i, Manuel and Huber, Bernd A. and Mart\'in, Fernando and Cederquist, Henrik and Zettergren, Henning and Rousseau, Patrick and D\'iaz-Tendero, Sergio",
    	journal = "Phys. Rev. A",
    	volume = 90,
    	issue = 3,
    	pages = 032701,
    	numpages = 11,
    	year = 2014,
    	publisher = "American Physical Society",
    	doi = "10.1103/PhysRevA.90.032701",
    	url = "http://link.aps.org/doi/10.1103/PhysRevA.90.032701"
    }
    
  17. M Gatchell, P Rousseau, A Domaracka, M H Stockett, T Chen, H T Schmidt, J Y Chesnel, A Méry, S Maclot, L Adoui, B A Huber, H Zettergren and H Cederquist.
    Ions colliding with mixed clusters of C60 and coronene: Fragmentation and bond formation. Phys. Rev. A 90:022713, 2014.
    URL, DOI BibTeX

    @article{PhysRevA.90.022713,
    	title = "Ions colliding with mixed clusters of C60 and coronene: Fragmentation and bond formation",
    	author = "Gatchell, M. and Rousseau, P. and Domaracka, A. and Stockett, M. H. and Chen, T. and Schmidt, H. T. and Chesnel, J. Y. and M\'ery, A. and Maclot, S. and Adoui, L. and Huber, B. A. and Zettergren, H. and Cederquist, H.",
    	journal = "Phys. Rev. A",
    	volume = 90,
    	issue = 2,
    	pages = 022713,
    	numpages = 7,
    	year = 2014,
    	publisher = "American Physical Society",
    	doi = "10.1103/PhysRevA.90.022713",
    	url = "http://link.aps.org/doi/10.1103/PhysRevA.90.022713"
    }
    
  18. Henning Zettergren, Fredrik Linden and Henrik Cederquist.
    Comment on "Surface-charge distribution on a dielectric sphere due to an external point charge: examples of C60 and C240 fullerenes, Phys. Chem. Chem. Phys., 2013, 15, 20115". Phys. Chem. Chem. Phys., pages -, 2014.
    URL, DOI BibTeX

    @article{C4CP02036G,
    	author = "Zettergren, Henning and Linden, Fredrik and Cederquist, Henrik",
    	doi = "10.1039/C4CP02036G",
    	journal = "Phys. Chem. Chem. Phys.",
    	pages = "-",
    	publisher = "The Royal Society of Chemistry",
    	title = {Comment on {"}Surface-charge distribution on a dielectric sphere due to an external point charge: examples of C60 and C240 fullerenes{,} Phys. Chem. Chem. Phys.{,} 2013{,} 15{,} 20115{"}},
    	url = "http://dx.doi.org/10.1039/C4CP02036G",
    	year = 2014,
    	bdsk-url-1 = "http://dx.doi.org/10.1039/C4CP02036G"
    }
    
  19. Y Wang, H Zettergren, P Rousseau, T Chen, M Gatchell, M H Stockett, A Domaracka, L Adoui, B A Huber, H Cederquist, M Alcamí and F Martín.
    Formation dynamics of fullerene dimers $C_118^+$, $C_119^+$, and $C_120^+$. Phys. Rev. A 89:062708, June 2014.
    URL, DOI BibTeX

    @article{PhysRevA.89.062708,
    	title = "Formation dynamics of fullerene dimers ${C}_{118}^{+}$, ${C}_{119}^{+}$, and ${C}_{120}^{+}$",
    	author = "Wang, Y. and Zettergren, H. and Rousseau, P. and Chen, T. and Gatchell, M. and Stockett, M. H. and Domaracka, A. and Adoui, L. and Huber, B. A. and Cederquist, H. and Alcam{\'i}, M. and Mart{\'i}n, F.",
    	journal = "Phys. Rev. A",
    	volume = 89,
    	issue = 6,
    	pages = 062708,
    	numpages = 12,
    	year = 2014,
    	month = "Jun",
    	publisher = "American Physical Society",
    	doi = "10.1103/PhysRevA.89.062708",
    	url = "http://link.aps.org/doi/10.1103/PhysRevA.89.062708"
    }
    
  20. T Chen, M Gatchell, M H Stockett, J D Alexander, Y Zhang, P Rousseau, A Domaracka, S Maclot, R Delaunay, L Adoui, B A Huber, T Schlathölter, H T Schmidt, H Cederquist and H Zettergren.
    Absolute fragmentation cross sections in atom-molecule collisions: Scaling laws for non-statistical fragmentation of polycyclic aromatic hydrocarbon molecules. The Journal of Chemical Physics 140(22):224306, 2014.
    URL, DOI BibTeX

    @article{:/content/aip/journal/jcp/140/22/10.1063/1.4881603,
    	author = {Chen, T. and Gatchell, M. and Stockett, M. H. and Alexander, J. D. and Zhang, Y. and Rousseau, P. and Domaracka, A. and Maclot, S. and Delaunay, R. and Adoui, L. and Huber, B. A. and Schlath{\"o}lter, T. and Schmidt, H. T. and Cederquist, H. and Zettergren, H.},
    	doi = "http://dx.doi.org/10.1063/1.4881603",
    	eid = 224306,
    	journal = "The Journal of Chemical Physics",
    	number = 22,
    	pages = 224306,
    	title = "Absolute fragmentation cross sections in atom-molecule collisions: Scaling laws for non-statistical fragmentation of polycyclic aromatic hydrocarbon molecules",
    	url = "http://scitation.aip.org/content/aip/journal/jcp/140/22/10.1063/1.4881603",
    	volume = 140,
    	year = 2014,
    	bdsk-url-1 = "http://scitation.aip.org/content/aip/journal/jcp/140/22/10.1063/1.4881603",
    	bdsk-url-2 = "http://dx.doi.org/10.1063/1.4881603"
    }
    
  21. M Gatchell, M H Stockett, P Rousseau, T Chen, K Kulyk, H T Schmidt, J Y Chesnel, A Domaracka, A Méry, S Maclot, L Adoui, K Støchkel, P Hvelplund, Y Wang, M Alcamí, B A Huber, F Martín, H Zettergren and H Cederquist.
    Non-statistical fragmentation of PAHs and fullerenes in collisions with atoms. International Journal of Mass Spectrometry 365–366(0):260 - 265, 2014.
    URL, DOI BibTeX

    @article{Gatchell2014260,
    	author = "M. Gatchell and M.H. Stockett and P. Rousseau and T. Chen and K. Kulyk and H.T. Schmidt and J.Y. Chesnel and A. Domaracka and A. M{\'e}ry and S. Maclot and L. Adoui and K. St{\o}chkel and P. Hvelplund and Y. Wang and M. Alcam{\'i} and B.A. Huber and F. Mart{\'i}n and H. Zettergren and H. Cederquist",
    	doi = "http://dx.doi.org/10.1016/j.ijms.2013.12.013",
    	issn = "1387-3806",
    	journal = "International Journal of Mass Spectrometry",
    	keywords = "Non-statistical fragmentation",
    	note = "Special issue: Tilmann mark",
    	number = 0,
    	pages = "260 - 265",
    	title = "Non-statistical fragmentation of \{PAHs\} and fullerenes in collisions with atoms",
    	url = "http://www.sciencedirect.com/science/article/pii/S1387380613004491",
    	volume = "365--366",
    	year = 2014,
    	bdsk-url-1 = "http://www.sciencedirect.com/science/article/pii/S1387380613004491",
    	bdsk-url-2 = "http://dx.doi.org/10.1016/j.ijms.2013.12.013"
    }
    
  22. M H Stockett, H Zettergren, L Adoui, J D Alexander, U Berzins, T Chen, M Gatchell, N Haag, B A Huber, P Hvelplund, A Johansson, H A B Johansson, K Kulyk, S Rosen, P Rousseau, K Stochkel, H T Schmidt and H Cederquist.
    Nonstatistical fragmentation of large molecules. PHYSICAL REVIEW A 89(3), 2014.
    DOI BibTeX

    @article{ISI:000332340800004,
    	article-number = "{032701}",
    	author = "Stockett, M. H. and Zettergren, H. and Adoui, L. and Alexander, J. D. and Berzins, U. and Chen, T. and Gatchell, M. and Haag, N. and Huber, B. A. and Hvelplund, P. and Johansson, A. and Johansson, H. A. B. and Kulyk, K. and Rosen, S. and Rousseau, P. and Stochkel, K. and Schmidt, H. T. and Cederquist, H.",
    	doi = "{10.1103/PhysRevA.89.032701}",
    	eissn = "{1094-1622}",
    	issn = "{1050-2947}",
    	journal = "{PHYSICAL REVIEW A}",
    	month = "{MAR 6}",
    	number = "{3}",
    	title = "{Nonstatistical fragmentation of large molecules}",
    	unique-id = "{ISI:000332340800004}",
    	volume = "{89}",
    	year = "{2014}",
    	bdsk-url-1 = "http://dx.doi.org/10.1103/PhysRevA.89.032701%7D"
    }
    
  23. G Reitsma, H Zettergren, L Boschman, E Bodewits, R Hoekstra and T Schlathölter.
    Ion–polycyclic aromatic hydrocarbon collisions: kinetic energy releases for specific fragmentation channels. Journal of Physics B: Atomic, Molecular and Optical Physics 46(24):245201, 2013.
    URL BibTeX

    @article{0953-4075-46-24-245201,
    	author = "G Reitsma and H Zettergren and L Boschman and E Bodewits and R Hoekstra and T Schlathölter",
    	title = "Ion–polycyclic aromatic hydrocarbon collisions: kinetic energy releases for specific fragmentation channels",
    	journal = "Journal of Physics B: Atomic, Molecular and Optical Physics",
    	volume = 46,
    	number = 24,
    	pages = 245201,
    	url = "http://stacks.iop.org/0953-4075/46/i=24/a=245201",
    	year = 2013
    }
    
  24. F Seitz, H Zettergren, P Rousseau, Y Wang, T Chen, M Gatchell, J D Alexander, M H Stockett, J Rangama, J Y Chesnel, M Capron, J C Poully, A Domaracka, A Mery, S Maclot, V Vizcaino, H T Schmidt, L Adoui, M Alcami, A G G M Tielens, F Martin, B A Huber and H Cederquist.
    Ions colliding with clusters of fullerenes–-Decay pathways and covalent bond formations. The Journal of Chemical Physics 139(3):034309, 2013.
    URL, DOI BibTeX

    @article{seitz:034309,
    	author = "F. Seitz and H. Zettergren and P. Rousseau and Y. Wang and T. Chen and M. Gatchell and J. D. Alexander and M. H. Stockett and J. Rangama and J. Y. Chesnel and M. Capron and J. C. Poully and A. Domaracka and A. Mery and S. Maclot and V. Vizcaino and H. T. Schmidt and L. Adoui and M. Alcami and A. G. G. M. Tielens and F. Martin and B. A. Huber and H. Cederquist",
    	collaboration = "",
    	title = "Ions colliding with clusters of fullerenes---Decay pathways and covalent bond formations",
    	publisher = "AIP",
    	year = 2013,
    	journal = "The Journal of Chemical Physics",
    	volume = 139,
    	number = 3,
    	eid = 034309,
    	numpages = 8,
    	pages = 034309,
    	keywords = "argon; bonds (chemical); charge exchange; evaporation; excited states; fullerenes; helium ions; ionisation; ion-molecule collisions; ion-molecule reactions; molecular clusters; molecular dynamics method; Monte Carlo methods; positive ions; van der Waals forces; xenon",
    	url = "/images/articles/Cov_bond_form_JCP.html",
    	doi = "10.1063/1.4812790"
    }
    
  25. H T Schmidt, R D Thomas, M Gatchell, S Rosén, P Reinhed, P Löfgren, L Brännholm, M Blom, M Björkhage, E Bäckström, J D Alexander, S Leontein, D Hanstorp, H Zettergren, L Liljeby, A Källberg, A Simonsson, F Hellberg, S Mannervik, M Larsson, W D Geppert, K G Rensfelt, H Danared, A Paál, M Masuda, P Halldén, G Andler, M H Stockett, T Chen, G Källersjö, J Weimer, K Hansen, H Hartman and H Cederquist.
    First storage of ion beams in the Double Electrostatic Ion-Ring Experiment: DESIREE. Review of Scientific Instruments 84(5):055115, 2013.
    URL, DOI BibTeX

    @article{schmidt:055115,
    	author = {H. T. Schmidt and R. D. Thomas and M. Gatchell and S. Ros\'{e}n and P. Reinhed and P. L\"{o}fgren and L. Br\"{a}nnholm and M. Blom and M. Bj\"{o}rkhage and E. B\"{a}ckstr\"{o}m and J. D. Alexander and S. Leontein and D. Hanstorp and H. Zettergren and L. Liljeby and A. K\"{a}llberg and A. Simonsson and F. Hellberg and S. Mannervik and M. Larsson and W. D. Geppert and K. G. Rensfelt and H. Danared and A. Pa\'{a}l and M. Masuda and P. Halld\'{e}n and G. Andler and M. H. Stockett and T. Chen and G. K\"{a}llersj\"{o} and J. Weimer and K. Hansen and H. Hartman and H. Cederquist},
    	collaboration = "",
    	title = "First storage of ion beams in the Double Electrostatic Ion-Ring Experiment: DESIREE",
    	publisher = "AIP",
    	year = 2013,
    	journal = "Review of Scientific Instruments",
    	volume = 84,
    	number = 5,
    	eid = 055115,
    	numpages = 6,
    	pages = 055115,
    	keywords = "ion accelerators; ion beams; particle beam injection; space charge; storage rings",
    	url = "/images/articles/DESIREE_Comm_RSI.html",
    	doi = "10.1063/1.4807702"
    }
    
  26. H Zettergren, P Rousseau, Y Wang, F Seitz, T Chen, M Gatchell, J D Alexander, M H Stockett, J Rangama, J Y Chesnel, M Capron, J C Poully, A Domaracka, A Mery, S Maclot, H T Schmidt, L Adoui, M Alcami, A G G M Tielens, F Martin, B A Huber and H Cederquist.
    Formations of Dumbbell C118 and C119 inside Clusters of C60 Molecules by Collision with alpha Particles. Phys. Rev. Lett. 110:185501, May 2013.
    URL, DOI BibTeX

    @article{PhysRevLett.110.185501,
    	title = "Formations of Dumbbell C118 and C119 inside Clusters of C60 Molecules by Collision with alpha Particles",
    	author = "Zettergren, H. and Rousseau, P. and Wang, Y. and Seitz, F. and Chen, T. and Gatchell, M. and Alexander, J. D. and Stockett, M. H. and Rangama, J. and Chesnel, J. Y. and Capron, M. and Poully, J. C. and Domaracka, A. and Mery, A. and Maclot, S. and Schmidt, H. T. and Adoui, L. and Alcami, M. and Tielens, A. G. G. M. and Martin, F. and Huber, B. A. and Cederquist, H.",
    	journal = "Phys. Rev. Lett.",
    	volume = 110,
    	issue = 18,
    	pages = 185501,
    	numpages = 5,
    	year = 2013,
    	month = "May",
    	doi = "10.1103/PhysRevLett.110.185501",
    	url = "http://link.aps.org/doi/10.1103/PhysRevLett.110.185501",
    	publisher = "American Physical Society"
    }
    
  27. B O Forsberg, J D Alexander, T Chen, A T Pettersson, M Gatchell, H Cederquist and H Zettergren.
    Ions interacting with planar aromatic molecules: Modeling electron transfer reactions. JOURNAL OF CHEMICAL PHYSICS 138(5), 2013.
    DOI BibTeX

    @article{ ISI:000314746400029,
    	author = "Forsberg, B. O. and Alexander, J. D. and Chen, T. and Pettersson, A. T. and Gatchell, M. and Cederquist, H. and Zettergren, H.",
    	title = "{Ions interacting with planar aromatic molecules: Modeling electron transfer reactions}",
    	journal = "{JOURNAL OF CHEMICAL PHYSICS}",
    	year = "{2013}",
    	volume = "{138}",
    	number = "{5}",
    	month = "{FEB 7}",
    	abstract = "{We present theoretical absolute charge exchange cross sections for multiply charged cations interacting with the Polycyclic Aromatic Hydrocarbon (PAH) molecules pyrene C14H10, coronene C24H12, or circumcoronene C54H18. These planar, nearly circular, PAHs are modelled as conducting, infinitely thin, and perfectly circular discs, which are randomly oriented with respect to straight line ion trajectories. We present the analytical solution for the potential energy surface experienced by an electron in the field of such a charged disc and a point-charge at an arbitrary position. The location and height of the corresponding potential energy barrier from this simple model are in close agreement with those from much more computationally demanding Density Functional Theory (DFT) calculations in a number of test cases. The model results compare favourably with available experimental data on single-and multiple electron transfer reactions and we demonstrate that it is important to include the orientation dependent polarizabilities of the molecules (model discs) in particular for the larger PAHs. PAH ionization energy sequences from DFT are tabulated and used as model inputs. Absolute cross sections for the ionization of PAH molecules, and PAH ionization energies such as the ones presented here may be useful when considering the roles of PAHs and their ions in, e. g., interstellar chemistry, stellar atmospheres, and in related photoabsorption and photoemission spectroscopies. (C) 2013 American Institute of Physics. {[}http://dx.doi.org/10.1063/1.4790164]}",
    	doi = "{10.1063/1.4790164}",
    	article-number = "{054306}",
    	issn = "{0021-9606}",
    	unique-id = "{ISI:000314746400029}"
    }
    
  28. G Reitsma, H Zettergren, S Martin, R Bredy, L Chen, J Bernard, R Hoekstra and T Schlatholter.
    Activation energies for fragmentation channels of anthracene dications-experiment and theory. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS 45(21), 2012.
    DOI BibTeX

    @article{ ISI:000309589100010,
    	author = "Reitsma, G. and Zettergren, H. and Martin, S. and Bredy, R. and Chen, L. and Bernard, J. and Hoekstra, R. and Schlatholter, T.",
    	title = "{Activation energies for fragmentation channels of anthracene dications-experiment and theory}",
    	journal = "{JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS}",
    	year = "{2012}",
    	volume = "{45}",
    	number = "{21}",
    	month = "{NOV 14}",
    	abstract = "{We have studied the fragmentation of the polycyclic aromatic hydrocarbon anthracene (C14H10) after double electron transfer to a 5 keV proton. The excitation energies leading to the most relevant dissociation and fission channels of the resulting molecular dication were directly determined experimentally. Density functional theory calculations were performed to explore the potential energy surfaces on which the fragmentation dynamics proceed. There is clear experimental evidence for a dominance of fission into C11H7+-C3H3+ over C2H2+ loss. The energetic ordering of the dissociation and fission channels and the kinetic energy releases are in good agreement with the theoretical results. It can be concluded that the unique combination of experiment and theory presented here is an excellent tool to study the fragmentation of complex molecular ions in unprecedented detail.}",
    	doi = "{10.1088/0953-4075/45/21/215201}",
    	article-number = "{215201}",
    	issn = "{0953-4075}",
    	unique-id = "{ISI:000309589100010}"
    }
    
  29. P Rousseau, A Lawicki, A I S Holm, M Capron, R Maisonny, S Maclot, E Lattouf, H A B Johansson, F Seitz, A Mery, J Rangama, H Zettergren, S Rosen, H T Schmidt, J -Y Chesnel, A Domaracka, B Manil, L Adoui, H Cederquist and B A Huber.
    Low-energy ions interacting with anthracene molecules and clusters. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 279:140-143, 2012.
    DOI BibTeX

    @article{ ISI:000303637500033,
    	author = "Rousseau, P. and Lawicki, A. and Holm, A. I. S. and Capron, M. and Maisonny, R. and Maclot, S. and Lattouf, E. and Johansson, H. A. B. and Seitz, F. and Mery, A. and Rangama, J. and Zettergren, H. and Rosen, S. and Schmidt, H. T. and Chesnel, J. -Y. and Domaracka, A. and Manil, B. and Adoui, L. and Cederquist, H. and Huber, B. A.",
    	title = "{Low-energy ions interacting with anthracene molecules and clusters}",
    	journal = "{NUCLEAR INSTRUMENTS \& METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS}",
    	year = "{2012}",
    	volume = "{279}",
    	pages = "{140-143}",
    	month = "{MAY 15}",
    	note = "{5th International Conference on Elementary Processes in Atomic Systems (CEPAS), Belgrade, SERBIA, JUN 21-25, 2011}",
    	organization = "{Univ Belgrade, Inst Phys; Serbian Acad Sci \& Arts (SASA); Republ Serbia, Minist Educ \& Sci; Serbian Phys Soc; Serv Cooperat dact culturelle Ambassade France Serbie; Osterreichisches Kulturforum Belgrad}",
    	abstract = "{The interaction of slow ions (nu similar to 0.4 au.) with a small polycyclic aromatic hydrocarbon, namely anthracene (C14H10), is studied in the gas-phase either with the isolated molecule or with a pure cluster target. We discuss the ionization and fragmentation of the molecule with respect to the projectile charge state, i.e. for singly charged He+ ions and for multiply charged Xe20+. ions. For the isolated C14H10, single or multiple ionization of the molecule occurs under ion impact. The (multi) cation relative yields are compared with those obtained by other ionization methods (electron and fs-laser). The molecular dissociation occurs by loss of hydrogen and small hydrocarbon molecules, leading to the formation of CnHx cations. The interaction of Xe20+ with C14H10 clusters gives surprising results, i.e. the emission of hotter monomer compared to the interaction with He+. (C) 2011 Elsevier B.V. All rights reserved.}",
    	doi = "{10.1016/j.nimb.2011.10.050}",
    	issn = "{0168-583X}",
    	researcherid-numbers = "{Lawicki, Arkadiusz/G-2541-2011}",
    	unique-id = "{ISI:000303637500033}"
    }
    
  30. Orla Kelly, Christopher R Calvert, Jason B Greenwood, Henning Zettergren, Steen Brondsted Nielsen and Jean A Wyer.
    Effects of Charge Location on the Absorptions and Lifetimes of Protonated Tyrosine Peptides in Vacuo. JOURNAL OF PHYSICAL CHEMISTRY A 116(7):1701-1709, 2012.
    DOI BibTeX

    @article{ ISI:000301156100003,
    	author = "Kelly, Orla and Calvert, Christopher R. and Greenwood, Jason B. and Zettergren, Henning and Nielsen, Steen Brondsted and Wyer, Jean A.",
    	title = "{Effects of Charge Location on the Absorptions and Lifetimes of Protonated Tyrosine Peptides in Vacuo}",
    	journal = "{JOURNAL OF PHYSICAL CHEMISTRY A}",
    	year = "{2012}",
    	volume = "{116}",
    	number = "{7}",
    	pages = "{1701-1709}",
    	month = "{FEB 23}",
    	abstract = "{Nearby charges affect the electronic energy levels of chromophores, with the extent of the effect being determined by the magnitude of the charge and degree of charge-chromophore separation. The molecular configuration dictates the charge chromophore distance. Hence, in this study, we aim to assess how the location of the charge influences the absorption of a set of model protonated and diprotonated peptide ions, and whether spectral differences are large enough to be identified. The studied ions were the dipeptide YK, the tripeptide KYK (Y = tyrosine; K = lysine) and their complexes with 18-crown-6-ether (CE). The CE targets the ammonium group by forming internal ionic hydrogen bonds and limits the folding of the peptide. In the tripeptide, the distance between the chromophore and the backbone ammonium is enlarged relative to that in the dipeptide. Experiments were performed in an electrostatic ion storage ring using a tunable laser system, and action spectra based on lifetime measurements were obtained in the range from 210 to 310 nm. The spectra are all quite similar though there seems to be some changes in the absorption band between 210 and 250 nm, while in the lower energy band all ions had a maximum absorption at similar to 275 nm. Lifetimes after photoexcitation were found to shorten upon protonation and lengthen upon CE complexation, in accordance with the increased number of degrees of freedom and an increase in activation energies for dissociation as the mobile proton model is no longer operative.}",
    	doi = "{10.1021/jp208578w}",
    	issn = "{1089-5639}",
    	unique-id = "{ISI:000301156100003}"
    }
    
  31. Christian Leidlmair, Yang Wang, Peter Bartl, Harald Schoebel, Stephan Denifl, Michael Probst, Manuel Alcami, Fernando Martin, Henning Zettergren, Klavs Hansen, Olof Echt and Paul Scheier.
    Structures, Energetics, and Dynamics of Helium Adsorbed on Isolated Fullerene Ions. PHYSICAL REVIEW LETTERS 108(6), 2012.
    DOI BibTeX

    @article{ ISI:000300246000014,
    	author = "Leidlmair, Christian and Wang, Yang and Bartl, Peter and Schoebel, Harald and Denifl, Stephan and Probst, Michael and Alcami, Manuel and Martin, Fernando and Zettergren, Henning and Hansen, Klavs and Echt, Olof and Scheier, Paul",
    	title = "{Structures, Energetics, and Dynamics of Helium Adsorbed on Isolated Fullerene Ions}",
    	journal = "{PHYSICAL REVIEW LETTERS}",
    	year = "{2012}",
    	volume = "{108}",
    	number = "{6}",
    	month = "{FEB 13}",
    	abstract = "{Helium adsorbed on C-60(+) and C-70(+) exhibits phenomena akin to helium on graphite. Mass spectra suggest that commensurate layers form when all carbon hexagons and pentagons are occupied by one He each, but that the solvation shell does not close until 60 He atoms are adsorbed on C-60(+), or 62 on C-70(+). Molecular dynamics simulations of C60Hen+ at 4 K show that the commensurate phase is solid. Helium added to C60He32+ will displace some atoms from pentagonal sites, leading to coexistence of a registered layer of immobile atoms interlaced with a nonregistered layer of mobile atoms.}",
    	doi = "{10.1103/PhysRevLett.108.076101}",
    	article-number = "{076101}",
    	issn = "{0031-9007}",
    	researcherid-numbers = "{Alcami, Manuel/F-1366-2010 Hansen, Klavs/J-1959-2012}",
    	unique-id = "{ISI:000300246000014}"
    }
    
  32. Henning Zettergren and Henrik Cederquist.
    {Comment on “Treating highly charged carbon and fullerene clusters as dielectric particles” by A. J. Stace and E. Bichoutskaia, Phys. Chem. Chem. Phys., 2011, 13, 18339}. PHYSICAL CHEMISTRY CHEMICAL PHYSICS 14(48):16770, 2012.
    DOI BibTeX

    @article{ ISI:000311735700033,
    	author = "Zettergren, Henning and Cederquist, Henrik",
    	title = "{Comment on ``Treating highly charged carbon and fullerene clusters as dielectric particles{''} by A. J. Stace and E. Bichoutskaia, Phys. Chem. Chem. Phys., 2011, 13, 18339}",
    	journal = "{PHYSICAL CHEMISTRY CHEMICAL PHYSICS}",
    	year = "{2012}",
    	volume = "{14}",
    	number = "{48}",
    	pages = "{16770}",
    	doi = "{10.1039/c2cp42883k}",
    	issn = "{1463-9076}",
    	unique-id = "{ISI:000311735700033}"
    }
    
  33. Henning Zettergren, Bjorn O Forsberg and Henrik Cederquist.
    Are single C-60 fullerenes dielectric or metallic?. PHYSICAL CHEMISTRY CHEMICAL PHYSICS 14(47):16360-16364, 2012.
    DOI BibTeX

    @article{ ISI:000311161700024,
    	author = "Zettergren, Henning and Forsberg, Bjorn O. and Cederquist, Henrik",
    	title = "{Are single C-60 fullerenes dielectric or metallic?}",
    	journal = "{PHYSICAL CHEMISTRY CHEMICAL PHYSICS}",
    	year = "{2012}",
    	volume = "{14}",
    	number = "{47}",
    	pages = "{16360-16364}",
    	abstract = "{We present analytical solutions for the interaction energies between a static point charge and a metal- or a dielectric sphere. These solutions include polarization effects to infinite orders in the inverse of the distance between the point charge and the spheres. Further, we present Density Functional Theory (DFT) calculations of interaction energies for a point charge in ranges of fixed positions outside a neutral or a singly charged C-60 molecule. Based on these DFT results, we conclude that the metal sphere model describes the electronic response of the C60 molecule much better than the dielectric sphere model. These findings are particularly important for calculations of energy barriers for charge transfer in reactions involving C60 molecules. The metal- and dielectric models should further be useful for descriptions of, for example, the polarizabilities of and interactions with conducting and insulating spherical clusters or particles.}",
    	doi = "{10.1039/c2cp42884a}",
    	issn = "{1463-9076}",
    	researcherid-numbers = "{Forsberg, Bjorn/K-4789-2012}",
    	unique-id = "{ISI:000311161700024}"
    }
    
  34. H A B Johansson, H Zettergren, A I S Holm, F Seitz, H T Schmidt, P Rousseau, A Lawicki, M Capron, A Domaracka, E Lattouf, S Maclot, R Maisonny, B Manil, J -Y Chesnel, L Adoui, B A Huber and H Cederquist.
    Ionization and fragmentation of polycyclic aromatic hydrocarbon clusters in collisions with keV ions. PHYSICAL REVIEW A 84(4), 2011.
    DOI BibTeX

    @article{ ISI:000295712700013,
    	author = "Johansson, H. A. B. and Zettergren, H. and Holm, A. I. S. and Seitz, F. and Schmidt, H. T. and Rousseau, P. and Lawicki, A. and Capron, M. and Domaracka, A. and Lattouf, E. and Maclot, S. and Maisonny, R. and Manil, B. and Chesnel, J. -Y. and Adoui, L. and Huber, B. A. and Cederquist, H.",
    	title = "{Ionization and fragmentation of polycyclic aromatic hydrocarbon clusters in collisions with keV ions}",
    	journal = "{PHYSICAL REVIEW A}",
    	year = "{2011}",
    	volume = "{84}",
    	number = "{4}",
    	month = "{OCT 10}",
    	abstract = "{We report on an experimental study of the ionization and fragmentation of clusters of k polycyclic aromatic hydrocarbon (PAH) molecules using anthracene, C14H10, or coronene, C24H12. These PAH clusters are moderately charged and strongly heated in small impact parameter collisions with 22.5-keV He2+ ions, after which they mostly decay in long monomer evaporation sequences with singly charged and comparatively cold monomers as dominating end products. We describe a simple cluster evaporation model and estimate the number of PAH molecules in the clusters that have to be hit by He2+ projectiles for such complete cluster evaporations to occur. Highly charged and initially cold clusters are efficiently formed in collisions with 360-keV Xe20+ ions, leading to cluster Coulomb explosions and several hot charged fragments, which again predominantly yield singly charged, but much hotter, monomer ions than the He2+ collisions. We present a simple formula, based on density-functional-theory calculations, for the ionization energy sequences as functions of coronene cluster size, rationalized in terms of the classic electrostatic expression for the ionization of a charged conducting object. Our analysis indicates that multiple electron removal by highly charged ions from a cluster of PAH molecules rapidly may become more important than single ionization as the cluster size k increases and that this is the main reason for the unexpectedly strong heating in these types of collisions.}",
    	doi = "{10.1103/PhysRevA.84.043201}",
    	article-number = "{043201}",
    	issn = "{1050-2947}",
    	researcherid-numbers = "{Lawicki, Arkadiusz/G-2541-2011}",
    	unique-id = "{ISI:000295712700013}"
    }
    
  35. H A B Johansson, H Zettergren, A I S Holm, N Haag, Brondsted S Nielsen, J A Wyer, M -B S Kirketerp, K Stochkel, P Hvelplund, H T Schmidt and H Cederquist.
    Unimolecular dissociation of anthracene and acridine cations: The importance of isomerization barriers for the C2H2 loss and HCN loss channels. JOURNAL OF CHEMICAL PHYSICS 135(8), 2011.
    DOI BibTeX

    @article{ ISI:000294484700036,
    	author = "Johansson, H. A. B. and Zettergren, H. and Holm, A. I. S. and Haag, N. and Nielsen, S. Brondsted and Wyer, J. A. and Kirketerp, M. -B. S. and Stochkel, K. and Hvelplund, P. and Schmidt, H. T. and Cederquist, H.",
    	title = "{Unimolecular dissociation of anthracene and acridine cations: The importance of isomerization barriers for the C2H2 loss and HCN loss channels}",
    	journal = "{JOURNAL OF CHEMICAL PHYSICS}",
    	year = "{2011}",
    	volume = "{135}",
    	number = "{8}",
    	month = "{AUG 28}",
    	abstract = "{The loss of C2H2 is a low activation energy dissociation channel for anthracene (C14H10) and acridine (C13H9N) cations. For the latter ion another prominent fragmentation pathway is the loss of HCN. We have studied these two dissociation channels by collision induced dissociation experiments of 50 keV anthracene cations and protonated acridine, both produced by electrospray ionization, in collisions with a neutral xenon target. In addition, we have carried out density functional theory calculations on possible reaction pathways for the loss of C2H2 and HCN. The mass spectra display features of multi-step processes, and for protonated acridine the dominant first step process is the loss of a hydrogen from the N site, which then leads to C2H2/HCN loss from the acridine cation. With our calculations we have identified three pathways for the loss of C2H2 from the anthracene cation, with three different cationic products: 2-ethynylnaphthalene, biphenylene, and acenaphthylene. The third product is the one with the overall lowest dissociation energy barrier. For the acridine cation our calculated pathway for the loss of C2H2 leads to the 3-ethynylquinoline cation, and the loss of HCN leads to the biphenylene cation. Isomerization plays an important role in the formation of the non-ethynyl containing products. All calculated fragmentation pathways should be accessible in the present experiment due to substantial energy deposition in the collisions. (C) 2011 American Institute of Physics. {[}doi:10.1063/1.3626792]}",
    	doi = "{10.1063/1.3626792}",
    	article-number = "{084304}",
    	issn = "{0021-9606}",
    	unique-id = "{ISI:000294484700036}"
    }
    
  36. F Seitz, A I S Holm, H Zettergren, H A B Johansson, S Rosen, H T Schmidt, A Lawicki, J Rangama, P Rousseau, M Capron, R Maisonny, A Domaracka, L Adoui, A Mery, B Manil, B A Huber and H Cederquist.
    Polycyclic aromatic hydrocarbon-isomer fragmentation pathways: Case study for pyrene and fluoranthene molecules and clusters. JOURNAL OF CHEMICAL PHYSICS 135(6), 2011.
    DOI BibTeX

    @article{ ISI:000293955000012,
    	author = "Seitz, F. and Holm, A. I. S. and Zettergren, H. and Johansson, H. A. B. and Rosen, S. and Schmidt, H. T. and Lawicki, A. and Rangama, J. and Rousseau, P. and Capron, M. and Maisonny, R. and Domaracka, A. and Adoui, L. and Mery, A. and Manil, B. and Huber, B. A. and Cederquist, H.",
    	title = "{Polycyclic aromatic hydrocarbon-isomer fragmentation pathways: Case study for pyrene and fluoranthene molecules and clusters}",
    	journal = "{JOURNAL OF CHEMICAL PHYSICS}",
    	year = "{2011}",
    	volume = "{135}",
    	number = "{6}",
    	month = "{AUG 14}",
    	abstract = "{We report on measurements of the ionization and fragmentation of polycyclic aromatic hydrocarbon (PAH) targets in Xe(20+) + C(16)H(10) and Xe(20+) + {[}C(16)H(10)](k) collisions and compare results for the two C(16)H(10) isomers: pyrene and fluoranthene. For both types of targets, i.e., for single PAH molecules isolated in vacuum or for isomerically pure clusters of one of the molecules, the resulting fragment spectra are surprisingly similar. However, we do observe weak but significant isomer effects. Although these are manifested in very different ways for the monomer and cluster targets, they both have at their roots small differences (<2.5 eV) between the total binding energies of neutral, and singly and multiply charged pyrene and fluoranthene monomers. The results will be discussed in view of the density functional theory calculations of ionization and dissociation energies for fluoranthene and pyrene. A simple classical over-the-barrier model is used to estimate cross sections for single-and multiple-electron transfer between PAHs and ions. Calculated single and multiple ionization energies, and the corresponding model PAH ionization cross sections, are given. (C) 2011 American Institute of Physics. {[}doi: 10.1063/1.3622589]}",
    	doi = "{10.1063/1.3622589}",
    	article-number = "{064302}",
    	issn = "{0021-9606}",
    	researcherid-numbers = "{Lawicki, Arkadiusz/G-2541-2011}",
    	unique-id = "{ISI:000293955000012}"
    }
    
  37. R D Thomas, H T Schmidt, G Andler, M Bjorkhage, M Blom, L Brannholm, E Backstrom, H Danared, S Das, N Haag, P Hallden, F Hellberg, A I S Holm, H A B Johansson, A Kallberg, G Kallersjo, M Larsson, S Leontein, L Liljeby, P Lofgren, B Malm, S Mannervik, M Masuda, D Misra, A Orban, A Paal, P Reinhed, K -G Rensfelt, S Rosen, K Schmidt, F Seitz, A Simonsson, J Weimer, H Zettergren and H Cederquist.
    The double electrostatic ion ring experiment: A unique cryogenic electrostatic storage ring for merged ion-beams studies. REVIEW OF SCIENTIFIC INSTRUMENTS 82(6), June 2011.
    DOI BibTeX

    @article{ ISI:000292334000069,
    	author = "Thomas, R. D. and Schmidt, H. T. and Andler, G. and Bjorkhage, M. and Blom, M. and Brannholm, L. and Backstrom, E. and Danared, H. and Das, S. and Haag, N. and Hallden, P. and Hellberg, F. and Holm, A. I. S. and Johansson, H. A. B. and Kallberg, A. and Kallersjo, G. and Larsson, M. and Leontein, S. and Liljeby, L. and Lofgren, P. and Malm, B. and Mannervik, S. and Masuda, M. and Misra, D. and Orban, A. and Paal, A. and Reinhed, P. and Rensfelt, K. -G. and Rosen, S. and Schmidt, K. and Seitz, F. and Simonsson, A. and Weimer, J. and Zettergren, H. and Cederquist, H.",
    	title = "{The double electrostatic ion ring experiment: A unique cryogenic electrostatic storage ring for merged ion-beams studies}",
    	journal = "{REVIEW OF SCIENTIFIC INSTRUMENTS}",
    	year = "{2011}",
    	volume = "{82}",
    	number = "{6}",
    	month = "{JUN}",
    	abstract = "{We describe the design of a novel type of storage device currently under construction at Stockholm University, Sweden, using purely electrostatic focussing and deflection elements, in which ion beams of opposite charges are confined under extreme high vacuum cryogenic conditions in separate ``rings{''} and merged over a common straight section. The construction of this double electrostatic ion ring experiment uniquely allows for studies of interactions between cations and anions at low and well-defined internal temperatures and centre-of-mass collision energies down to about 10 K and 10 meV, respectively. Position sensitive multi-hit detector systems have been extensively tested and proven to work in cryogenic environments and these will be used to measure correlations between reaction products in, for example, electron-transfer processes. The technical advantages of using purely electrostatic ion storage devices over magnetic ones are many, but the most relevant are: electrostatic elements which are more compact and easier to construct; remanent fields, hysteresis, and eddy-currents, which are of concern in magnetic devices, are no longer relevant; and electrical fields required to control the orbit of the ions are not only much easier to create and control than the corresponding magnetic fields, they also set no upper mass limit on the ions that can be stored. These technical differences are a boon to new areas of fundamental experimental research, not only in atomic and molecular physics but also in the boundaries of these fields with chemistry and biology. For examples, studies of interactions with internally cold molecular ions will be particular useful for applications in astrophysics, while studies of solvated ionic clusters will be of relevance to aeronomy and biology. (C) 2011 American Institute of Physics. {[}doi:10.1063/1.3602928]}",
    	doi = "{10.1063/1.3602928}",
    	article-number = "{065112}",
    	issn = "{0034-6748}",
    	researcherid-numbers = "{Misra, Deepankar/C-8813-2009}",
    	unique-id = "{ISI:000292334000069}"
    }
    
  38. A Lawicki, A I S Holm, P Rousseau, M Capron, R Maisonny, S Maclot, F Seitz, H A B Johansson, S Rosen, H T Schmidt, H Zettergren, B Manil, L Adoui, H Cederquist and B A Huber.
    Multiple ionization and fragmentation of isolated pyrene and coronene molecules in collision with ions. PHYSICAL REVIEW A 83(2), 2011.
    DOI BibTeX

    @article{ ISI:000287076800006,
    	author = "Lawicki, A. and Holm, A. I. S. and Rousseau, P. and Capron, M. and Maisonny, R. and Maclot, S. and Seitz, F. and Johansson, H. A. B. and Rosen, S. and Schmidt, H. T. and Zettergren, H. and Manil, B. and Adoui, L. and Cederquist, H. and Huber, B. A.",
    	title = "{Multiple ionization and fragmentation of isolated pyrene and coronene molecules in collision with ions}",
    	journal = "{PHYSICAL REVIEW A}",
    	year = "{2011}",
    	volume = "{83}",
    	number = "{2}",
    	month = "{FEB 8}",
    	abstract = "{The interaction of multiply charged ions (He(2+), O(3+), and Xe(20+)) with gas-phase pericondensed polycyclic aromatic hydrocarbon (PAH) molecules of coronene (C(24)H(12)) and pyrene (C(16)H(10)) is studied for low-velocity collisions (v <= 0.6 a.u.). The mass spectrometric analysis shows that singly and up to quadruply charged intact molecules are important reaction products. The relative experimental yields are compared with the results of a simple classical over-the-barrier model. For higher molecular charge states, the experimental yields decrease much more strongly than the model predictions due to the instabilities of the multiply charged PAH molecules. Even-odd oscillations with the number of carbon atoms, n, in the intensity distributions of the C(n)H(x)(+) fragments indicate a linear chain structure of the fragments similar to those observed for ion-C(60) collisions. The latter oscillations are known to be due to dissociation energy differences between even-and odd-n C(n)-chain molecules. For PAH molecules, the average numbers of H atoms attached to the C(n)H(x) chains are larger for even-n reflecting acetylenic bond systems.}",
    	doi = "{10.1103/PhysRevA.83.022704}",
    	article-number = "{022704}",
    	issn = "{1050-2947}",
    	researcherid-numbers = "{Lawicki, Arkadiusz/G-2541-2011}",
    	unique-id = "{ISI:000287076800006}"
    }
    
  39. A I S Holm, H A B Johansson, H Cederquist and H Zettergren.
    Dissociation and multiple ionization energies for five polycyclic aromatic hydrocarbon molecules. JOURNAL OF CHEMICAL PHYSICS 134(4), 2011.
    DOI BibTeX

    @article{ ISI:000286897600044,
    	author = "Holm, A. I. S. and Johansson, H. A. B. and Cederquist, H. and Zettergren, H.",
    	title = "{Dissociation and multiple ionization energies for five polycyclic aromatic hydrocarbon molecules}",
    	journal = "{JOURNAL OF CHEMICAL PHYSICS}",
    	year = "{2011}",
    	volume = "{134}",
    	number = "{4}",
    	month = "{JAN 28}",
    	abstract = "{We have performed density functional theory calculations for a range of neutral, singly, and multiply charged polycyclic aromatic hydrocarbons (PAHs), and their fragmentation products for H-, H(+)-, C(2)H(2)-, and C(2)H(2)(+)-emissions. The adiabatic and vertical ionization energies follow linear dependencies as functions of charge state for all five intact PAHs (naphthalene, biphenylene, anthracene, pyrene, and coronene). First estimates of the total ionization and fragmentation cross sections in ion-PAH collisions display markedly different size dependencies for pericondensed and catacondensed PAH species, reflecting differences in their first ionization energies. The dissociation energies show that the PAH(q+)-molecules are thermodynamically stable for q <= 2 (naphthalene, biphenylene, and anthracene), q <= 3 (pyrene), and q <= 4 (coronene). PAHs in charge states above these limits may also survive experimental time scales due to the presence of reaction barriers as deduced from explorations of the potential energy surface regions for H(+)-emissions from all five PAHs and for C(2)H(2)(+)-emission from naphthalene - the smallest PAH. (C) 2011 American Institute of Physics. {[}doi:10.1063/1.3541252]}",
    	doi = "{10.1063/1.3541252}",
    	article-number = "{044301}",
    	issn = "{0021-9606}",
    	unique-id = "{ISI:000286897600044}"
    }
    
  40. N Haag, A I S Holm, H A B Johansson, H Zettergren, H T Schmidt, Brondsted S Nielsen, P Hvelplund and H Cederquist.
    Electron capture induced dissociation of doubly protonated pentapeptides: Dependence on molecular structure and charge separation. JOURNAL OF CHEMICAL PHYSICS 134(3), 2011.
    DOI BibTeX

    @article{ ISI:000286472200071,
    	author = "Haag, N. and Holm, A. I. S. and Johansson, H. A. B. and Zettergren, H. and Schmidt, H. T. and Nielsen, S. Brondsted and Hvelplund, P. and Cederquist, H.",
    	title = "{Electron capture induced dissociation of doubly protonated pentapeptides: Dependence on molecular structure and charge separation}",
    	journal = "{JOURNAL OF CHEMICAL PHYSICS}",
    	year = "{2011}",
    	volume = "{134}",
    	number = "{3}",
    	month = "{JAN 21}",
    	abstract = "{We have studied electron capture induced dissociation of a set of doubly protonated pentapeptides, all composed of one lysine (K) and either four glycine (G) or four alanine (A) residues, as a function of the sequence of these building blocks. Thereby the separation of the two charges, sequestered on the N-terminal amino group and the lysine side chain, is varied. The characteristic cleavage of N-C(alpha) bonds is observed for all peptides over the whole backbone length, with the charge carrying fragments always containing K. The resulting fragmentation patterns are very similar if G is replaced by A. In the case of {[}XKXXX+2H](2+) (X=A or G), a distinct feature is observed in the distribution of backbone cleavage fragments and the probability for ammonia loss is drastically reduced. This may be due to an isomer with an amide oxygen as protonation site giving rise to the observed increase in breakage at a specific site in the molecule. For the other peptides, a correlation with the distance between amide oxygen and the charge at the lysine side chain has been found. This may be an indication that it is only the contribution from this site to the charge stabilization of the amide pi{*} orbitals which determines relative fragment intensities. For comparison, complexes with two crown ether molecules have been studied as well. The crown ether provides a shielding of the charge and prevents the peptide from folding and internal hydrogen bonding, which leads to a more uniform fragmentation behavior. (C) 2011 American Institute of Physics. {[}doi:10.1063/1.3533952]}",
    	doi = "{10.1063/1.3533952}",
    	article-number = "{035102}",
    	issn = "{0021-9606}",
    	unique-id = "{ISI:000286472200071}"
    }
    
  41. A I S Holm, H Zettergren, H A B Johansson, F Seitz, S Rosen, H T Schmidt, A Lawicki, J Rangama, P Rousseau, M Capron, R Maisonny, L Adoui, A Mery, B Manil, B A Huber and H Cederquist.
    Ions Colliding with Cold Polycyclic Aromatic Hydrocarbon Clusters. PHYSICAL REVIEW LETTERS 105(21), 2010.
    DOI BibTeX

    @article{ ISI:000284407400012,
    	author = "Holm, A. I. S. and Zettergren, H. and Johansson, H. A. B. and Seitz, F. and Rosen, S. and Schmidt, H. T. and Lawicki, A. and Rangama, J. and Rousseau, P. and Capron, M. and Maisonny, R. and Adoui, L. and Mery, A. and Manil, B. and Huber, B. A. and Cederquist, H.",
    	title = "{Ions Colliding with Cold Polycyclic Aromatic Hydrocarbon Clusters}",
    	journal = "{PHYSICAL REVIEW LETTERS}",
    	year = "{2010}",
    	volume = "{105}",
    	number = "{21}",
    	month = "{NOV 19}",
    	abstract = "{We report the first experimental study of ions interacting with clusters of polycyclic aromatic hydrocarbon (PAH) molecules. Collisions between 11.25 keV He-3(+) or 360 keV Xe-129(20+) and weakly bound clusters of one of the smallest PAH molecules, anthracene, show that C14H10 clusters have much higher tendencies to fragment in ion collisions than other weakly bound clusters. The ionization is dominated by peripheral collisions in which the clusters, very surprisingly, are more strongly heated by Xe20+ collisions than by He+ collisions. The appearance size is k = 15 for {[}C14H10](k)(2+).}",
    	doi = "{10.1103/PhysRevLett.105.213401}",
    	article-number = "{213401}",
    	issn = "{0031-9007}",
    	researcherid-numbers = "{Lawicki, Arkadiusz/G-2541-2011}",
    	unique-id = "{ISI:000284407400012}"
    }
    
  42. H Zettergren, H A B Johansson, H T Schmidt, J Jensen, P Hvelplund, S Tomita, Y Wang, F Martin, M Alcami, B Manil, L Maunoury, B A Huber and H Cederquist.
    Magic and hot giant fullerenes formed inside ion irradiated weakly bound C-60 clusters. JOURNAL OF CHEMICAL PHYSICS 133(10), 2010.
    DOI BibTeX

    @article{ ISI:000282475400015,
    	author = "Zettergren, H. and Johansson, H. A. B. and Schmidt, H. T. and Jensen, J. and Hvelplund, P. and Tomita, S. and Wang, Y. and Martin, F. and Alcami, M. and Manil, B. and Maunoury, L. and Huber, B. A. and Cederquist, H.",
    	title = "{Magic and hot giant fullerenes formed inside ion irradiated weakly bound C-60 clusters}",
    	journal = "{JOURNAL OF CHEMICAL PHYSICS}",
    	year = "{2010}",
    	volume = "{133}",
    	number = "{10}",
    	month = "{SEP 14}",
    	abstract = "{We find that the most stable fullerene isomers, C-70-C-94, form efficiently in close-to central collisions between keV atomic ions and weakly bound clusters of more than 15 C-60-molecules. We observe extraordinarily high yields of C-70 and marked preferences for C-78 and C-84. Larger even-size carbon molecules, C-96-C-180, follow a smooth log-normal (statistical) intensity distribution. Measurements of kinetic energies indicate that C-70-C-94 mainly are formed by coalescence reactions between small carbon molecules and Coo, while C-n with n >= 96 are due to self-assembly (of small molecules) and shrinking hot giant fullerenes. (C) 2010 American Institute of Physics. {[}doi:10.1063/1.3479584]}",
    	doi = "{10.1063/1.3479584}",
    	article-number = "{104301}",
    	issn = "{0021-9606}",
    	researcherid-numbers = "{Alcami, Manuel/F-1366-2010}",
    	unique-id = "{ISI:000282475400015}"
    }
    
  43. Maj-Britt Suhr Kirketerp, Michael Axman Petersen, Marius Wanko, Henning Zettergren, Angel Rubio, Mogens Brondsted Nielsen and Steen Brondsted Nielsen.
    Double-Bond versus Triple-Bond Bridges: Does it Matter for the Charge-Transfer Absorption by Donor-Acceptor Chromophores?. CHEMPHYSCHEM 11(12):2495-2498, 2010.
    DOI BibTeX

    @article{ ISI:000281691100003,
    	author = "Kirketerp, Maj-Britt Suhr and Petersen, Michael Axman and Wanko, Marius and Zettergren, Henning and Rubio, Angel and Nielsen, Mogens Brondsted and Nielsen, Steen Brondsted",
    	title = "{Double-Bond versus Triple-Bond Bridges: Does it Matter for the Charge-Transfer Absorption by Donor-Acceptor Chromophores?}",
    	journal = "{CHEMPHYSCHEM}",
    	year = "{2010}",
    	volume = "{11}",
    	number = "{12}",
    	pages = "{2495-2498}",
    	month = "{AUG 23}",
    	doi = "{10.1002/cphc.201000464}",
    	issn = "{1439-4235}",
    	researcherid-numbers = "{Petersen, Michael /C-7379-2009 Wanko, Marius/A-5526-2010 Rubio, Angel/A-5507-2008 Computing Service, IZO-SGI/F-3072-2010 CSIC-UPV/EHU, CFM/F-4867-2012}",
    	orcid-numbers = "{Rubio, Angel/0000-0003-2060-3151 }",
    	unique-id = "{ISI:000281691100003}"
    }
    
  44. Frantisek Turecek, Thomas W Chung, Christopher L Moss, Jean A Wyer, Anneli Ehlerding, Anne I S Holm, Henning Zettergren, Steen Brondsted Nielsen, Preben Hvelplund, Julia Chamot-Rooke, Benjamin Bythell and Bela Paizs.
    The Histidine Effect. Electron Transfer and Capture Cause Different Dissociations and Rearrangements of Histidine Peptide Cation-Radicals. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 132(31):10728-10740, 2010.
    DOI BibTeX

    @article{ ISI:000280692200031,
    	author = "Turecek, Frantisek and Chung, Thomas W. and Moss, Christopher L. and Wyer, Jean A. and Ehlerding, Anneli and Holm, Anne I. S. and Zettergren, Henning and Nielsen, Steen Brondsted and Hvelplund, Preben and Chamot-Rooke, Julia and Bythell, Benjamin and Paizs, Bela",
    	title = "{The Histidine Effect. Electron Transfer and Capture Cause Different Dissociations and Rearrangements of Histidine Peptide Cation-Radicals}",
    	journal = "{JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}",
    	year = "{2010}",
    	volume = "{132}",
    	number = "{31}",
    	pages = "{10728-10740}",
    	month = "{AUG 11}",
    	abstract = "{Electron-transfer and -capture dissociations of doubly protonated peptides gave dramatically different product ions for a series of histidine-containing pentapeptides of both non-tryptic (AAHAL, AHAAL, AHADL, AHDAL) and tryptic (AAAHK, AAHAK, AHAAK, HAAAK, AAAHR, AAHAR, AHAAR, HAAAR) type. Electron transfer from gaseous Cs atoms and fluoranthene anions triggered backbone dissociations of all four N-C(alpha) bonds in the peptide ions in addition to loss of H and NH(3). Substantial fractions of charge-reduced cation-radicals did not dissociate on an experimental time scale ranging from 10(-6) to 10(-1) s. Multistage tandem mass spectrometric (MS(n)) experiments indicated that the non-dissociating cation-radicals had undergone rearrangements. These were explained as being due to proton migrations from N-terminal ammonium and COOH groups to the C-2' position of the reduced His ring, resulting in substantial radical stabilization. Ab initio calculations revealed that the charge-reduced cation-radicals can exist as low-energy zwitterionic amide pi{*} states which were local energy minima. These states underwent facile exothermic proton migrations to form aminoketyl radical intermediates, whereas direct N-C(alpha) bond cleavage in zwitterions was disfavored. RRKM analysis indicated that backbone N-C(alpha) bond cleavages did not occur competitively from a single charge-reduced precursor. Rather, these bond cleavages proceeded from distinct intermediates which originated from different electronic states accessed by electron transfer. In stark contrast to electron transfer, capture of a free electron by the peptide ions mainly induced radical dissociations of the charge-carrying side chains and loss of a hydrogen atom followed by standard backbone dissociations of even-electron ions. The differences in dissociation are explained by different electronic states being accessed upon electron transfer and capture.}",
    	doi = "{10.1021/ja907808h}",
    	issn = "{0002-7863}",
    	researcherid-numbers = "{Wyer, Jean/B-2455-2010 Chung, Thomas/C-2591-2011}",
    	unique-id = "{ISI:000280692200031}"
    }
    
  45. S Wethekam, H Zettergren, Ch. Linsmeier, H Cederquist and H Winter.
    Resonant electron capture by C-60 ions at a metal surface with projected band gap. PHYSICAL REVIEW B 81(12), March 2010.
    DOI BibTeX

    @article{ ISI:000276248900036,
    	author = "Wethekam, S. and Zettergren, H. and Linsmeier, Ch. and Cederquist, H. and Winter, H.",
    	title = "{Resonant electron capture by C-60 ions at a metal surface with projected band gap}",
    	journal = "{PHYSICAL REVIEW B}",
    	year = "{2010}",
    	volume = "{81}",
    	number = "{12}",
    	month = "{MAR}",
    	abstract = "{C-60(+) and C-60(2+) ions are scattered under grazing incidence from an atomically clean and flat Be(0001) surface at kilo-electron-volt energies. Distances for electron transfer are deduced from shifts of angular distributions for incident C-60(+) and C-60(2+) projectiles, which reflect changes in the interaction potentials at the instants of electron transfers. These distances are consistent with classical over-the-barrier model results indicating that the suppression of charge transfer, observed for atomic projectiles in front of metal surfaces with a projected band gap, is absent for fullerenes.}",
    	doi = "{10.1103/PhysRevB.81.121416}",
    	article-number = "{121416}",
    	issn = "{1098-0121}",
    	unique-id = "{ISI:000276248900036}"
    }
    
  46. Anneli Ehlerding, Jean Ann Wyer, Henning Zettergren, Maj-Britt Suhr Kirketerp and Steen Brondsted Nielsen.
    UV Photodissociation of Protonated Gly-Trp and Trp-Gly Dipeptides and Their Complexes with Crown Ether in an Electrostatic Ion Storage Ring. JOURNAL OF PHYSICAL CHEMISTRY A 114(1):299-303, 2010.
    DOI BibTeX

    @article{ ISI:000273268900035,
    	author = "Ehlerding, Anneli and Wyer, Jean Ann and Zettergren, Henning and Kirketerp, Maj-Britt Suhr and Nielsen, Steen Brondsted",
    	title = "{UV Photodissociation of Protonated Gly-Trp and Trp-Gly Dipeptides and Their Complexes with Crown Ether in an Electrostatic Ion Storage Ring}",
    	journal = "{JOURNAL OF PHYSICAL CHEMISTRY A}",
    	year = "{2010}",
    	volume = "{114}",
    	number = "{1}",
    	pages = "{299-303}",
    	month = "{JAN 14}",
    	abstract = "{{Photodissociation of protonated GW, WG (G = glycine",
    	w = "",
    	doi = "{10.1021/jp9086317}",
    	issn = "{1089-5639}",
    	researcherid-numbers = "{Wyer, Jean/B-2455-2010}",
    	unique-id = "{ISI:000273268900035}"
    }
    
  47. Frantisek Turecek, Subhasis Panja, Jean A Wyer, Anneli Ehlerding, Henning Zettergren, Steen Brondsted Nielsen, Preben Hvelplund, Benjamin Bythell and Bela Paizs.
    Carboxyl-Catalyzed Prototropic Rearrangements in Histidine Peptide Radicals upon Electron Transfer: Effects of Peptide Sequence and Conformation. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 131(45):16472-16487, 2009.
    DOI BibTeX

    @article{ ISI:000271723000041,
    	author = "Turecek, Frantisek and Panja, Subhasis and Wyer, Jean A. and Ehlerding, Anneli and Zettergren, Henning and Nielsen, Steen Brondsted and Hvelplund, Preben and Bythell, Benjamin and Paizs, Bela",
    	title = "{Carboxyl-Catalyzed Prototropic Rearrangements in Histidine Peptide Radicals upon Electron Transfer: Effects of Peptide Sequence and Conformation}",
    	journal = "{JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}",
    	year = "{2009}",
    	volume = "{131}",
    	number = "{45}",
    	pages = "{16472-16487}",
    	month = "{NOV 18}",
    	abstract = "{We report an unusual prototropic rearrangement in gas-phase radicals formed by collisional electron transfer from cesium atoms to protonated peptides HAL, AHL, and ALH at 50 keV. The rearrangement depends on the peptide amino acid sequence and presence or steric accessibility of a free carboxyl group. Upon electron transfer, protonated HAL and ALH rearrange to tautomers that are detected as nondissociated anions in charge-reversal mass spectra. The isomerization is minor in protonated ALH and virtually absent in HAL amide. Electron structure calculations indicate that the gas-phase ions are preferentially protonated in the His imidazole ring and consist of multiple conformers that differ in their hydrogen bonding patterns. Electron transfer to protonated HAL and AHL triggers an exothermic and dynamically barrierless transfer of the carboxyl proton onto the C-2' position of the His ring that occurs on a 120-240 ns time scale. The kinetics of this isomerization are controlled by internal rotations in the radicals to assume conformations favoring the proton transfer. The radical conformations also affect subsequent proton migrations in zwitterionic His imidazoline intermediates that reform the COOH group and result in His ring isomerization. This autocatalytic prototropic rearrangement in gas-phase peptide radicals is analogous to enzyme catalytic reactions involving His and acidic amino acid residues. In contrast to HAL and AHL, the C-2' position is sterically inaccessible in ALH radicals. These radicals undergo proton migrations to the His ring C-5' positions that have moderate energy barriers and are less efficient. RRKM calculations on the combined B3LYP and PMP2/6-311++G(2d,p) potential energy surface of the ground doublet electronic state of the peptide radicals provided rate constants that were quantitatively consistent with the dissociations observed in the gas phase. The formation of minor sequence z(1) and z(2) fragments from AHL was interpreted as occurring in the first excited state of the radical.}",
    	doi = "{10.1021/ja9050229}",
    	issn = "{0002-7863}",
    	researcherid-numbers = "{Wyer, Jean/B-2455-2010}",
    	unique-id = "{ISI:000271723000041}"
    }
    
  48. Camilla Skinnerup Jensen, Anne I S Holm, Henning Zettergren, Jakob B Overgaard, Preben Hvelplund and Steen Brondsted Nielsen.
    On the Charge Partitioning Between c and z Fragments Formed After Electron-Capture Induced Dissociation of Charge-Tagged Lys-Lys and Ala-Lys Dipeptide Dications. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 20(10):1881-1889, October 2009.
    DOI BibTeX

    @article{ ISI:000271037300013,
    	author = "Jensen, Camilla Skinnerup and Holm, Anne I. S. and Zettergren, Henning and Overgaard, Jakob B. and Hvelplund, Preben and Nielsen, Steen Brondsted",
    	title = "{On the Charge Partitioning Between c and z Fragments Formed After Electron-Capture Induced Dissociation of Charge-Tagged Lys-Lys and Ala-Lys Dipeptide Dications}",
    	journal = "{JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY}",
    	year = "{2009}",
    	volume = "{20}",
    	number = "{10}",
    	pages = "{1881-1889}",
    	month = "{OCT}",
    	abstract = "{Here we report on the charge partition between c and z fragments formed after femtosecond collisional electron-transfer from Cs atoms to charge-tagged peptide dications. Peptides chosen for study were Ala-Lys (AK) and Lys-Lys (KK) where one or both of the lysine epsilon-amino groups were trimethylated to provide one or two fixed charges. For peptides with only one charge tag, the other charge was obtained by protonation of an amino group. In some experiments the ammonium group was tagged by 18-crown-6-ether (CE). Since recombination energies decrease in the order: MeNH(3)(+) > NMe(4)(+) > MeNH(3)(+)(CE) > NMe(4)(+)(CE), it is possible to change the probability for the transferred electron to end up at either the N-terminal or the C-terminal residue by CE attachment. We find, however, that the individual recombination energies have little influence on the relative ratio between the yield of c and z ions as long as there are no mobile protons that can be transferred between the two fragments. Our results can be accounted for by the Utah-Washington model where the electron is captured into an amide pi(star) orbital that weakens the N-C(alpha) bond and causes its breakage, followed by proton, electron, or hydrogen transfer between the c and z fragments that stay together as an ion-molecule complex for some time. The data are also in accordance with the notion that an amide group competes with the charged groups for the electron. Electron capture by charged groups results in loss of small neutrals such as hydrogen and ammonia. (J Am Soc Mass Spectrom 2009, 20, 1881-1889) (C) 2009 Published by Elsevier Inc. on behalf of American Society for Mass Spectrometry.}",
    	doi = "{10.1016/j.jasms.2009.06.015}",
    	issn = "{1044-0305}",
    	researcherid-numbers = "{Byskov, Camilla Skinnerup/G-5447-2012}",
    	unique-id = "{ISI:000271037300013}"
    }
    
  49. U Kadhane, M Perot, B Lucas, M Barat, J A Fayeton, C Jouvet, A Ehlerding, M -B S Kirketerp, Brondsted S Nielsen, J A Wyer and H Zettergren.
    Photodissociation of protonated tryptamine and its supramolecular complex with 18-crown-6 ether: Dissociation times and channels, absorption spectra, and excited states calculations. CHEMICAL PHYSICS LETTERS 480(1-3):57-61, 2009.
    DOI BibTeX

    @article{ ISI:000270083100011,
    	author = "Kadhane, U. and Perot, M. and Lucas, B. and Barat, M. and Fayeton, J. A. and Jouvet, C. and Ehlerding, A. and Kirketerp, M. -B. S. and Nielsen, S. Brondsted and Wyer, J. A. and Zettergren, H.",
    	title = "{Photodissociation of protonated tryptamine and its supramolecular complex with 18-crown-6 ether: Dissociation times and channels, absorption spectra, and excited states calculations}",
    	journal = "{CHEMICAL PHYSICS LETTERS}",
    	year = "{2009}",
    	volume = "{480}",
    	number = "{1-3}",
    	pages = "{57-61}",
    	month = "{SEP 28}",
    	abstract = "{Photodissociation of the complex between protonated tryptamine, TryH(+), and 18-crown-6 ether (CE) was investigated. Absorption maxima of TryH(+) and TryH(+)(CE) are at 249 and 273 nm, respectively. Ions decay exponentially on a microsecond timescale, and mass spectra reveal that NH(3) loss is an important channel even though CE targets this group. TD-DFT calculations identified an electronically excited state, where the photoactive electron is located in an antibonding orbital between C and NH(3). Dissociation along this coordinate and CE rearrangement to the new charge site accounts for ammonia loss. Photodissociation in an electric field and time-of-flight measurements corroborate such a non-statistical bond-breakage. (C) 2009 Elsevier B.V. All rights reserved.}",
    	doi = "{10.1016/j.cplett.2009.08.064}",
    	issn = "{0009-2614}",
    	researcherid-numbers = "{Wyer, Jean/B-2455-2010 jouvet, christophe/E-6985-2011}",
    	unique-id = "{ISI:000270083100011}"
    }
    
  50. Yang Wang, Henning Zettergren, Manuel Alcami and Fernando Martin.
    Stability of multiply charged fullerene anions and cations. PHYSICAL REVIEW A 80(3), September 2009.
    DOI BibTeX

    @article{ ISI:000270383900109,
    	author = "Wang, Yang and Zettergren, Henning and Alcami, Manuel and Martin, Fernando",
    	title = "{Stability of multiply charged fullerene anions and cations}",
    	journal = "{PHYSICAL REVIEW A}",
    	year = "{2009}",
    	volume = "{80}",
    	number = "{3}",
    	month = "{SEP}",
    	abstract = "{We present a systematic study of the stability of highly charged cationic and anionic fullerenes whose most stable neutral counterparts follow the isolated pentagon rule (IPR). In agreement with recent studies, we have found that, for many highly charged fullerenes, non-IPR isomers are significantly more stable than the IPR ones. To understand this behavior, we compare the results of elaborate density-functional theory (DFT) calculations to those of a simple Huckel molecular-orbital theory in which the DFT energies of the corresponding neutral systems are used as a reference. The model leads to a reasonable estimate of the relative stability of the IPR and non-IPR isomers as a function of charge, which can be used to identify, among the thousands of possible isomers and charge states, the non-IPR species that are likely more stable than the IPR isomers.}",
    	doi = "{10.1103/PhysRevA.80.033201}",
    	article-number = "{033201}",
    	issn = "{1050-2947}",
    	researcherid-numbers = "{Alcami, Manuel/F-1366-2010}",
    	unique-id = "{ISI:000270383900109}"
    }
    
  51. Jean Ann Wyer, Anneli Ehlerding, Henning Zettergren, Maj-Britt S Kirketerp and Steen Brondsted Nielsen.
    Tagging of Protonated Ala-Tyr and Tyr-Ala by Crown Ether Prevents Direct Hydrogen Loss and Proton Mobility after Photoexcitation: Importance for Gas-Phase Absorption Spectra, Dissociation Lifetimes, and Channels. JOURNAL OF PHYSICAL CHEMISTRY A 113(33):9277-9285, 2009.
    DOI BibTeX

    @article{ ISI:000268796800004,
    	author = "Wyer, Jean Ann and Ehlerding, Anneli and Zettergren, Henning and Kirketerp, Maj-Britt S. and Nielsen, Steen Brondsted",
    	title = "{Tagging of Protonated Ala-Tyr and Tyr-Ala by Crown Ether Prevents Direct Hydrogen Loss and Proton Mobility after Photoexcitation: Importance for Gas-Phase Absorption Spectra, Dissociation Lifetimes, and Channels}",
    	journal = "{JOURNAL OF PHYSICAL CHEMISTRY A}",
    	year = "{2009}",
    	volume = "{113}",
    	number = "{33}",
    	pages = "{9277-9285}",
    	month = "{AUG 20}",
    	abstract = "{{Photodissociation of protonated Tyr, Ala-Tyr, Tyr-Ala (Ala = alanine",
    	tyr = "",
    	doi = "{10.1021/jp904053d}",
    	issn = "{1089-5639}",
    	researcherid-numbers = "{Wyer, Jean/B-2455-2010}",
    	unique-id = "{ISI:000268796800004}"
    }
    
  52. Henning Zettergren, Lamri Adoui, Virgile Bernigaud, Henrik Cederquist, Nicole Haag, Anne I S Holm, Bernd A Huber, Preben Hvelplund, Henrik Johansson, Umesh Kadhane, Mikkel Koefoed Larsen, Bo Liu, Bruno Manil, Steen Brondsted Nielsen, Subhasis Panja, Jimmy Rangama, Peter Reinhed, Henning T Schmidt and Kristian Stochkel.
    Electron-Capture-Induced Dissociation of Microsolvated Di- and Tripeptide Monocations: Elucidation of Fragmentation Channels from Measurements of Negative Ions. CHEMPHYSCHEM 10(9-10):1619-1623, 2009.
    DOI BibTeX

    @article{ ISI:000267928100039,
    	author = "Zettergren, Henning and Adoui, Lamri and Bernigaud, Virgile and Cederquist, Henrik and Haag, Nicole and Holm, Anne I. S. and Huber, Bernd A. and Hvelplund, Preben and Johansson, Henrik and Kadhane, Umesh and Larsen, Mikkel Koefoed and Liu, Bo and Manil, Bruno and Nielsen, Steen Brondsted and Panja, Subhasis and Rangama, Jimmy and Reinhed, Peter and Schmidt, Henning T. and Stochkel, Kristian",
    	title = "{Electron-Capture-Induced Dissociation of Microsolvated Di- and Tripeptide Monocations: Elucidation of Fragmentation Channels from Measurements of Negative Ions}",
    	journal = "{CHEMPHYSCHEM}",
    	year = "{2009}",
    	volume = "{10}",
    	number = "{9-10}",
    	pages = "{1619-1623}",
    	month = "{JUL 13}",
    	abstract = "{{The results from an experimental study of bare and microsolvated peptide monocations in high-energy collision with cesium vapor are reported. Neutral radicals form after electron capture from cesium, which decay by H loss, NH, loss or N-C bond cleavage into characteristic z and c fragments. The neutral fragments are converted into negatively charged species in a second collision with cesium and are identified by means of mass spectrometry. For protonated GA (G = glycan",
    	a = "",
    	doi = "{10.1002/cphc.200800782}",
    	issn = "{1439-4235}",
    	unique-id = "{ISI:000267928100039}"
    }
    
  53. U Kadhane, J U Andersen, E Bonderup, B Concina, P Hvelplund, Suhr M -B Kirketerp, B Liu, Brondsted S Nielsen, S Panja, J Rangama, K Stochkel, S Tomita, H Zettergren, K Hansen, A E K Sunden, S E Canton, O Echt and J S Forster.
    Near-infrared photoabsorption by C-60 dianions in a storage ring. JOURNAL OF CHEMICAL PHYSICS 131(1), 2009.
    DOI BibTeX

    @article{ ISI:000267799100011,
    	author = "Kadhane, U. and Andersen, J. U. and Bonderup, E. and Concina, B. and Hvelplund, P. and Kirketerp, M. -B. Suhr and Liu, B. and Nielsen, S. Brondsted and Panja, S. and Rangama, J. and Stochkel, K. and Tomita, S. and Zettergren, H. and Hansen, K. and Sunden, A. E. K. and Canton, S. E. and Echt, O. and Forster, J. S.",
    	title = "{Near-infrared photoabsorption by C-60 dianions in a storage ring}",
    	journal = "{JOURNAL OF CHEMICAL PHYSICS}",
    	year = "{2009}",
    	volume = "{131}",
    	number = "{1}",
    	month = "{JUL 7}",
    	abstract = "{We present a detailed study of the electronic structure and the stability of C-60 dianions in the gas phase. Monoanions were extracted from a plasma source and converted to dianions by electron transfer in a Na vapor cell. The dianions were then stored in an electrostatic ring, and their near-infrared absorption spectrum was measured by observation of laser induced electron detachment. From the time dependence of the detachment after photon absorption, we conclude that the reaction has contributions from both direct electron tunneling to the continuum and vibrationally assisted tunneling after internal conversion. This implies that the height of the Coulomb barrier confining the attached electrons is at least similar to 1.5 eV. For C-60(2-) ions in solution electron spin resonance measurements have indicated a singlet ground state, and from the similarity of the absorption spectra we conclude that also the ground state of isolated C-60(2-) ions is singlet. The observed spectrum corresponds to an electronic transition from a t(1u) lowest unoccupied molecular orbital (LUMO) of C-60 to the t(1g) LUMO+1 level. The electronic levels of the dianion are split due to Jahn-Teller coupling to quadrupole deformations of the molecule, and a main absorption band at 10723 cm(-1) corresponds to a transition between the Jahn-Teller ground states. Also transitions from pseudorotational states with 200 cm(-1) and (probably) 420 cm(-1) excitation are observed. We argue that a very broad absorption band from about 11 500 cm(-1) to 13 500 cm(-1) consists of transitions to so-called cone states, which are Jahn-Teller states on a higher potential-energy surface, stabilized by a pseudorotational angular momentum barrier. A previously observed, high-lying absorption band for C-60(-) may also be a transition to a cone state.}",
    	doi = "{10.1063/1.3149775}",
    	article-number = "{014301}",
    	issn = "{0021-9606}",
    	researcherid-numbers = "{Sunden, Erika/F-2151-2011 Hansen, Klavs/J-1959-2012}",
    	unique-id = "{ISI:000267799100011}"
    }
    
  54. A E K Sunden, K Stochkel, S Panja, U Kadhane, P Hvelplund, Brondsted S Nielsen, H Zettergren, B Dynefors and K Hansen.
    Heat capacities of freely evaporating charged water clusters. JOURNAL OF CHEMICAL PHYSICS 130(22), 2009.
    DOI BibTeX

    @article{ ISI:000266968800016,
    	author = "Sunden, A. E. K. and Stochkel, K. and Panja, S. and Kadhane, U. and Hvelplund, P. and Nielsen, S. Brondsted and Zettergren, H. and Dynefors, B. and Hansen, K.",
    	title = "{Heat capacities of freely evaporating charged water clusters}",
    	journal = "{JOURNAL OF CHEMICAL PHYSICS}",
    	year = "{2009}",
    	volume = "{130}",
    	number = "{22}",
    	month = "{JUN 14}",
    	abstract = "{We report on evaporation studies on positively charged water clusters (H(+)(H(2)O)(N)) and negatively charged mixed clusters (X(-)(H(2)O)(N)) with a small core ion X (X=O(2), CO(3), or NO(3)), in the size range N=5-300. The clusters were produced by corona discharge in ambient air, accelerated to 50 keV and mass selected by an electromagnet. The loss of monomers during the subsequent 3.4 m free flight was recorded. The average losses are proportional to the clusters' heat capacities and this allowed the determination of size-dependent heat capacities. The values are found to increase almost linearly with clusters size for both species, with a rate of 6kB-8kB per added molecule. For clusters with N<21 the heat capacities per molecule are lower but the incremental increase higher. For N>21 the values are intermediate between the bulk liquid and the solid water 0 degrees C values. (C) 2009 American Institute of Physics. {[}DOI: 10.1063/1.3149784]}",
    	doi = "{10.1063/1.3149784}",
    	article-number = "{224308}",
    	issn = "{0021-9606}",
    	researcherid-numbers = "{Sunden, Erika/F-2151-2011 Hansen, Klavs/J-1959-2012}",
    	unique-id = "{ISI:000266968800016}"
    }
    
  55. Henning Zettergren, Yang Wang, Al Mokhtar Lamsabhi, Manuel Alcami and Fernando Martin.
    Density functional theory study of multiply ionized weakly bound fullerene dimers. JOURNAL OF CHEMICAL PHYSICS 130(22), 2009.
    DOI BibTeX

    @article{ ISI:000266968800010,
    	author = "Zettergren, Henning and Wang, Yang and Lamsabhi, Al Mokhtar and Alcami, Manuel and Martin, Fernando",
    	title = "{Density functional theory study of multiply ionized weakly bound fullerene dimers}",
    	journal = "{JOURNAL OF CHEMICAL PHYSICS}",
    	year = "{2009}",
    	volume = "{130}",
    	number = "{22}",
    	month = "{JUN 14}",
    	abstract = "{{Multiply ionized fullerene dimers ({[}C(60)](2)(q+)",
    	q = "",
    	doi = "{10.1063/1.3151683}",
    	article-number = "{224302}",
    	issn = "{0021-9606}",
    	researcherid-numbers = "{Lamsabhi, Al Mokhtar /A-5659-2010 Alcami, Manuel/F-1366-2010}",
    	orcid-numbers = "{Lamsabhi, Al Mokhtar /0000-0002-1509-2513 }",
    	unique-id = "{ISI:000266968800010}"
    }
    
  56. Maj-Britt Suhr Kirketerp, Michael Axman Petersen, Marius Wanko, Leonardo Andres Espinosa Leal, Henning Zettergren, Francisco M Raymo, Angel Rubio, Mogens Brondsted Nielsen and Steen Brondsted Nielsen.
    Absorption Spectra of 4-Nitrophenolate Ions Measured in Vacuo and in Solution. CHEMPHYSCHEM 10(8):1207-1209, 2009.
    DOI BibTeX

    @article{ ISI:000266954500008,
    	author = "Kirketerp, Maj-Britt Suhr and Petersen, Michael Axman and Wanko, Marius and Espinosa Leal, Leonardo Andres and Zettergren, Henning and Raymo, Francisco M. and Rubio, Angel and Nielsen, Mogens Brondsted and Nielsen, Steen Brondsted",
    	title = "{Absorption Spectra of 4-Nitrophenolate Ions Measured in Vacuo and in Solution}",
    	journal = "{CHEMPHYSCHEM}",
    	year = "{2009}",
    	volume = "{10}",
    	number = "{8}",
    	pages = "{1207-1209}",
    	month = "{JUN 2}",
    	doi = "{10.1002/cphc.200900174}",
    	issn = "{1439-4235}",
    	researcherid-numbers = "{Rubio, Angel/A-5507-2008 Petersen, Michael /C-7379-2009 espinosa leal, leonardo andres/F-4973-2010 Wanko, Marius/A-5526-2010 CSIC-UPV/EHU, CFM/F-4867-2012}",
    	orcid-numbers = "{Rubio, Angel/0000-0003-2060-3151 }",
    	unique-id = "{ISI:000266954500008}"
    }
    
  57. Anneli Ehlerding, Camilla S Jensen, Jean A Wyer, Anne I S Holm, Palle Jorgensen, Umesh Kadhane, Mikkel K Larsen, Subhasis Panja, Jean Christophe Poully, Esben S Worm, Henning Zettergren, Preben Hvelplund and Steen Brondsted Nielsen.
    Influence of temperature and crown ether complex formation on the charge partitioning between z and c fragments formed after electron capture by small peptide dications. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 282(1-2):21-27, 2009.
    DOI BibTeX

    @article{ ISI:000265307700004,
    	author = "Ehlerding, Anneli and Jensen, Camilla S. and Wyer, Jean A. and Holm, Anne I. S. and Jorgensen, Palle and Kadhane, Umesh and Larsen, Mikkel K. and Panja, Subhasis and Poully, Jean Christophe and Worm, Esben S. and Zettergren, Henning and Hvelplund, Preben and Nielsen, Steen Brondsted",
    	title = "{Influence of temperature and crown ether complex formation on the charge partitioning between z and c fragments formed after electron capture by small peptide dications}",
    	journal = "{INTERNATIONAL JOURNAL OF MASS SPECTROMETRY}",
    	year = "{2009}",
    	volume = "{282}",
    	number = "{1-2}",
    	pages = "{21-27}",
    	month = "{APR 15}",
    	abstract = "{{Electron capture by peptide dications results in N-C-alpha, bond cleavage to give c(+) and z or c and z(+) fragments. In this work we have investigated how crown ether (18-crown-6 = CE) complex formation and a change in the internal energy affect the charge division between the z and c fragments. Both complex formation and a high temperature have the effect of breaking internal ionic hydrogen bonds. The crown ether complex also lowers the probability of internal proton transfer between the two fragments, and reduces the recombination energy of the charged group it targets. The systems under study were doubly protonated di- and tripeptides, (AK+2H](2+), {[}AR+2H](2+), {[}KK+2H](2+) and {[}GHK+2H](2+) (A=alanine",
    	k = "",
    	g = "",
    	doi = "{10.1016/j.ijms.2009.01.019}",
    	issn = "{1387-3806}",
    	researcherid-numbers = "{Wyer, Jean/B-2455-2010 Byskov, Camilla Skinnerup/G-5447-2012}",
    	unique-id = "{ISI:000265307700004}"
    }
    
  58. Morten Kocks Lykkegaard, Henning Zettergren, Maj-Britt Suhr Kirketerp, Anneli Ehlerding, Jean Ann Wyer, Umesh Kadhane and Steen Brondsted Nielsen.
    Photodissociation of Isolated Ferric Heme and Heme-His Cations in an Electrostatic Ion Storage Ring. JOURNAL OF PHYSICAL CHEMISTRY A 113(8):1440-1444, 2009.
    DOI BibTeX

    @article{ ISI:000263529600006,
    	author = "Lykkegaard, Morten Kocks and Zettergren, Henning and Kirketerp, Maj-Britt Suhr and Ehlerding, Anneli and Wyer, Jean Ann and Kadhane, Umesh and Nielsen, Steen Brondsted",
    	title = "{Photodissociation of Isolated Ferric Heme and Heme-His Cations in an Electrostatic Ion Storage Ring}",
    	journal = "{JOURNAL OF PHYSICAL CHEMISTRY A}",
    	year = "{2009}",
    	volume = "{113}",
    	number = "{8}",
    	pages = "{1440-1444}",
    	month = "{FEB 26}",
    	abstract = "{Photodissociation of isolated Fe(III)-heme(+) and Fe(III)-heme(+)(His) ions in the gas phase has been investigated using an electrostatic storage ring. The experiment provides three pieces of information, namely fragmentation channels, dissociation times, and absorption spectra. After photoexcitation with either 390 or 532 nm light, we find that the fragmentation takes place on a microsecond to millisecond time scale, and the channels are CH(2)COOH loss (beta-cleavage reaction) and histidine loss from Fe(III)-heme(+) and Fe(III)-heme(+)(His), respectively. These channels were also observed by means of collision-induced dissociation. Significant information on the nonradiative processes that occur after photoexcitation was revealed from the decay spectra. At early times (first two to three milliseconds), the decay of the photoexcited ions is well-described by a statistical model based on an Arrhenius-type expression for the rate constant. The activation energy and preexponential factor are 1.9 +/- 0.2 eV and 1 x 10(17) to 1 x 10(21) s(-1) for heme(+) and 1.4 +/- 0.2 eV and 1 x 1016 to 1 x 10(19) s(-1) for heme(+)(His). Decay on a longer time scale was also observed and is ascribed to the population of lower-lying states with higher spin multiplicity because intersystem crossing back to the electronic ground-state is a bottleneck for the dissociation. The measurements give lifetimes for these lower-lying states of about 10 ms after 390 nm excitation and we estimate the probability of spin flip to be 0.3 and 0.8 for heme(+) and heme(+)(His), respectively.}",
    	doi = "{10.1021/jp809626v}",
    	issn = "{1089-5639}",
    	researcherid-numbers = "{Wyer, Jean/B-2455-2010}",
    	unique-id = "{ISI:000263529600006}"
    }
    
  59. Umesh Kadhane, Jens Ulrik Andersen, Anneli Ehlerding, Preben Hvelplund, Maj-Britt S Kirketerp, Morten Kocks Lykkegaard, Steen Brondsted Nielsen, Subhasis Panja, Jean Ann Wyer and Henning Zettergren.
    Photodissociation of protonated tryptophan and alteration of dissociation pathways by complexation with crown ether. JOURNAL OF CHEMICAL PHYSICS 129(18), 2008.
    DOI BibTeX

    @article{ ISI:000260944300023,
    	author = "Kadhane, Umesh and Andersen, Jens Ulrik and Ehlerding, Anneli and Hvelplund, Preben and Kirketerp, Maj-Britt S. and Lykkegaard, Morten Kocks and Nielsen, Steen Brondsted and Panja, Subhasis and Wyer, Jean Ann and Zettergren, Henning",
    	title = "{Photodissociation of protonated tryptophan and alteration of dissociation pathways by complexation with crown ether}",
    	journal = "{JOURNAL OF CHEMICAL PHYSICS}",
    	year = "{2008}",
    	volume = "{129}",
    	number = "{18}",
    	month = "{NOV 14}",
    	abstract = "{The behavior of protonated tryptophan (TrpH(+)) and its complex with 18-crown-6-ether (CE) after photoexcitation has been explored based on measurements of dissociation lifetimes, fragmentation channels, and absorption spectra using an electrostatic ion storage ring. A recent implementation of pulsed power supplies for the ring elements with microsecond response times allows us to identify the daughter ion fragment masses and to disentangle fragmentation that occurs from excited states immediately after photoexcitation from that occurring on a longer time scale of several microseconds to milliseconds. We find that attachment of crown ether significantly alters the dissociation channels since it renders the pi sigma({*})(NH(3)) state inaccessible and hence prevents the N-H bond breakage which is an important fragmentation channel of TrpH(+). As a result, on a long time scale (>10 mu s), photoexcited TrpH(+)(CE) decays exponentially whereas TrpH(+) displays a power-law decay. The only ions remaining in the latter case are Trp(+center dot) radical cations with a broad internal energy distribution caused by the departing hydrogen. Large changes in the fragment branching ratios as functions of excitation wavelength between 210 and 290 nm were found for both TrpH(+) and TrpH(+)(CE).}",
    	doi = "{10.1063/1.3009222}",
    	article-number = "{184304}",
    	issn = "{0021-9606}",
    	researcherid-numbers = "{Wyer, Jean/B-2455-2010}",
    	unique-id = "{ISI:000260944300023}"
    }
    
  60. Virgile Bernigaud, Henrik Cederquist, Nicole Haag, Anne I S Holm, Bernd A Huber, Preben Hvelplund, Umesh Kadhane, Mikkel Koefoed Larsen, Bruno Manil, Steen Brondsted Nielsen, Subhasis Panja, Sylwia Ptasinska, Jimmy Rangama, Peter Reinhed, Henning T Schmidt, Alexey V Streletskii, Kristian Stochkel, Esben S Worm and Henning Zettergren.
    Electron capture-induced dissociation of AK dipeptide dications: Influence of ion velocity, crown-ether complexation and collision gas. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 276(2-3):77-81, 2008.
    DOI BibTeX

    @article{ ISI:000259846000002,
    	author = "Bernigaud, Virgile and Cederquist, Henrik and Haag, Nicole and Holm, Anne I. S. and Huber, Bernd A. and Hvelplund, Preben and Kadhane, Umesh and Larsen, Mikkel Koefoed and Manil, Bruno and Nielsen, Steen Brondsted and Panja, Subhasis and Ptasinska, Sylwia and Rangama, Jimmy and Reinhed, Peter and Schmidt, Henning T. and Streletskii, Alexey V. and Stochkel, Kristian and Worm, Esben S. and Zettergren, Henning",
    	title = "{Electron capture-induced dissociation of AK dipeptide dications: Influence of ion velocity, crown-ether complexation and collision gas}",
    	journal = "{INTERNATIONAL JOURNAL OF MASS SPECTROMETRY}",
    	year = "{2008}",
    	volume = "{276}",
    	number = "{2-3}",
    	pages = "{77-81}",
    	month = "{OCT 1}",
    	abstract = "{The fragmentation of doubly protonated AK dipeptide ions has been investigated after collisional electron transfer. Electron capture leads to three dominant channels, H loss, NH3 loss, and N-C-alpha bond breakage to give either c(+) or z(+) fragment ions. The relative importance of these channels has been explored as a function of ion velocity, the degree of complexation with crown ether, and collision gas. Our results indicate that H loss and NH3 loss are competing channels whereas the probability of N-C-alpha bond breakage is more or less constant. (C) 2008 Elsevier B.V. All rights reserved.}",
    	doi = "{10.1016/j.ijms.2008.05.004}",
    	issn = "{1387-3806}",
    	unique-id = "{ISI:000259846000002}"
    }
    
  61. N Haag, Z Berenyi, P Reinhed, D Fischer, M Gudmundsson, H A B Johansson, H T Schmidt, H Cederquist and H Zettergren.
    Kinetic-energy-release distributions and barrier heights for C(2)a+ emission from multiply charged C(60) and C(70) fullerenes. PHYSICAL REVIEW A 78(4), October 2008.
    DOI BibTeX

    @article{ ISI:000260574100097,
    	author = "Haag, N. and Berenyi, Z. and Reinhed, P. and Fischer, D. and Gudmundsson, M. and Johansson, H. A. B. and Schmidt, H. T. and Cederquist, H. and Zettergren, H.",
    	title = "{Kinetic-energy-release distributions and barrier heights for C(2)a+ emission from multiply charged C(60) and C(70) fullerenes}",
    	journal = "{PHYSICAL REVIEW A}",
    	year = "{2008}",
    	volume = "{78}",
    	number = "{4}",
    	month = "{OCT}",
    	doi = "{10.1103/PhysRevA.78.043201}",
    	article-number = "{043201}",
    	issn = "{1050-2947}",
    	unique-id = "{ISI:000260574100097}"
    }
    
  62. Morten Kocks Lykkegaard, Anneli Ehlerding, Preben Hvelplund, Umesh Kadhane, Maj-Britt Suhr Kirketerp, Steen Brondsted Nielsen, Subhasis Panja, Jean Ann Wyer and Henning Zettergren.
    A soret marker band for four-coordinate ferric heme proteins from absorption spectra of isolated Fe(III)-Heme(+) and Fe(III)-Heme(+)(His) ions in vacuo. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 130(36):11856-11857, 2008.
    DOI BibTeX

    @article{ ISI:000258950500011,
    	author = "Lykkegaard, Morten Kocks and Ehlerding, Anneli and Hvelplund, Preben and Kadhane, Umesh and Kirketerp, Maj-Britt Suhr and Nielsen, Steen Brondsted and Panja, Subhasis and Wyer, Jean Ann and Zettergren, Henning",
    	title = "{A soret marker band for four-coordinate ferric heme proteins from absorption spectra of isolated Fe(III)-Heme(+) and Fe(III)-Heme(+)(His) ions in vacuo}",
    	journal = "{JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}",
    	year = "{2008}",
    	volume = "{130}",
    	number = "{36}",
    	pages = "{11856-11857}",
    	month = "{SEP 10}",
    	doi = "{10.1021/ja803460c}",
    	issn = "{0002-7863}",
    	researcherid-numbers = "{Wyer, Jean/B-2455-2010}",
    	unique-id = "{ISI:000258950500011}"
    }
    
  63. Henning T Schmidt, Henrik A B Johansson, Richard D Thomas, Wolf D Geppert, Nicole Haag, Peter Reinhed, Stefan Rosen, Mats Larsson, Hakan Danared, K -G Rensfelt, Leif Liljeby, Lars Bagge, Mikael Bjorkhage, Mikael Blom, Patrik Lofgren, Anders Kallberg, Ansgar Simonsson, Andras Paal, Henning Zettergren and Henrik Cederquist.
    DESIREE as a new tool for interstellar ion chemistry. INTERNATIONAL JOURNAL OF ASTROBIOLOGY 7(3-4):205-208, 2008.
    DOI BibTeX

    @article{ ISI:000273383100003,
    	author = "Schmidt, Henning T. and Johansson, Henrik A. B. and Thomas, Richard D. and Geppert, Wolf D. and Haag, Nicole and Reinhed, Peter and Rosen, Stefan and Larsson, Mats and Danared, Hakan and Rensfelt, K. -G. and Liljeby, Leif and Bagge, Lars and Bjorkhage, Mikael and Blom, Mikael and Lofgren, Patrik and Kallberg, Anders and Simonsson, Ansgar and Paal, Andras and Zettergren, Henning and Cederquist, Henrik",
    	title = "{DESIREE as a new tool for interstellar ion chemistry}",
    	journal = "{INTERNATIONAL JOURNAL OF ASTROBIOLOGY}",
    	year = "{2008}",
    	volume = "{7}",
    	number = "{3-4}",
    	pages = "{205-208}",
    	month = "{JUL-OCT}",
    	abstract = "{A novel cryogenic electrostatic storage device consisting of two ion-beam storage rings with a common straight section for studies of interactions between oppositely charged ions at low and well-defined relative velocities is under construction at Stockholm University. Here we consider the prospect Of using this new tool to measure cross-sections and rate coefficients for Mutual neutralization reactions of importance in interstellar ion chemistry in general and specifically in cosmic pre-biotic ion chemistry.}",
    	doi = "{10.1017/S1473550408004229}",
    	issn = "{1473-5504}",
    	unique-id = "{ISI:000273383100003}"
    }
    
  64. Henning Zettergren, Manuel Alcami and Fernando Martin.
    Stable non-IPR C-60 and C-70 fullerenes containing a uniform distribution of pyrenes and adjacent pentagons. CHEMPHYSCHEM 9(6):861-866, 2008.
    DOI BibTeX

    @article{ ISI:000255704100008,
    	author = "Zettergren, Henning and Alcami, Manuel and Martin, Fernando",
    	title = "{Stable non-IPR C-60 and C-70 fullerenes containing a uniform distribution of pyrenes and adjacent pentagons}",
    	journal = "{CHEMPHYSCHEM}",
    	year = "{2008}",
    	volume = "{9}",
    	number = "{6}",
    	pages = "{861-866}",
    	month = "{APR 21}",
    	abstract = "{The most abundant fullerenes, C-60 and C-70, and all the pure carbon fullerenes larger than C-70, follow the isolated-pentagon rule (IPR). Non-lPR fullerenes containing adjacent pentagons (APs) have been stabilized experimentally in cases where, according to Euler's theorem, it is topologically impossible to isolate A the pentagons from each other. Surprisingly, recent experiments have shown that a few endohedral fullerenes, for which IPR structures are possible, are stabilized in non-IPR cages. We show that, apart from strain, the physical property that governs the relative stabilities of fullerenes is the charge distribution in the cage. This charge distribution is controlled by the number and location of APs and pyrene motifs. We show that, when these motifs are uniformly distributed in the cage and well-separated from one other, stabilization of non-IPR endohedral and exohedral derivatives, as well as pure carbon fullerene anions and cations, is the rule, rather than the exception. This suggests that non-IPR derivatives might be even more common than IPR ones.}",
    	doi = "{10.1002/cphc.200700670}",
    	issn = "{1439-4235}",
    	researcherid-numbers = "{Alcami, Manuel/F-1366-2010}",
    	unique-id = "{ISI:000255704100008}"
    }
    
  65. B Liu, N Haag, H Johansson, H T Schmidt, H Cederquist, Brondsted S Nielsen, H Zettergren, P Hvelplund, B Manil and B A Huber.
    Electron capture induced dissociation of nucleotide anions in water nanodroplets. JOURNAL OF CHEMICAL PHYSICS 128(7), 2008.
    DOI BibTeX

    @article{ ISI:000253336800043,
    	author = "Liu, B. and Haag, N. and Johansson, H. and Schmidt, H. T. and Cederquist, H. and Nielsen, S. Brondsted and Zettergren, H. and Hvelplund, P. and Manil, B. and Huber, B. A.",
    	title = "{Electron capture induced dissociation of nucleotide anions in water nanodroplets}",
    	journal = "{JOURNAL OF CHEMICAL PHYSICS}",
    	year = "{2008}",
    	volume = "{128}",
    	number = "{7}",
    	month = "{FEB 21}",
    	abstract = "{We have studied the outcome of collisions between the hydrated nucleotide anion adenosine 5(')-monophosphate (AMP) and sodium. Electron capture leads to hydrogen loss as well as water evaporation regardless of the initial number m of water molecules attached to the parent ion (m <= 16). The yield of dianions with microsecond lifetimes increases strongly with m, which is explained from dielectric screening of the two charges by the water nanodroplet. For comparison, collision induced dissociation results in water losses with no or very little damage of the AMP molecule itself.}",
    	doi = "{10.1063/1.2839597}",
    	article-number = "{075102}",
    	issn = "{0021-9606}",
    	unique-id = "{ISI:000253336800043}"
    }
    
  66. Kristian Stochkel, Umesh Kadhane, Jens Ulrik Andersen, Anne I S Holm, Preben Hvelplund, Maj-Britt Suhr Kirketerp, Mikkel Koefoed Larsen, Morten Kocks Lykkegaard, Steen Brondsted Nielsen, Subhasis Panja and Henning Zettergren.
    A new technique for time-resolved daughter ion mass spectrometry on the microsecond to millisecond time scale using an electrostatic ion storage ring. REVIEW OF SCIENTIFIC INSTRUMENTS 79(2, 1), February 2008.
    DOI BibTeX

    @article{ ISI:000254194400008,
    	author = "Stochkel, Kristian and Kadhane, Umesh and Andersen, Jens Ulrik and Holm, Anne I. S. and Hvelplund, Preben and Kirketerp, Maj-Britt Suhr and Larsen, Mikkel Koefoed and Lykkegaard, Morten Kocks and Nielsen, Steen Brondsted and Panja, Subhasis and Zettergren, Henning",
    	title = "{A new technique for time-resolved daughter ion mass spectrometry on the microsecond to millisecond time scale using an electrostatic ion storage ring}",
    	journal = "{REVIEW OF SCIENTIFIC INSTRUMENTS}",
    	year = "{2008}",
    	volume = "{79}",
    	number = "{2, 1}",
    	month = "{FEB}",
    	abstract = "{A new method for time-resolved daughter ion mass spectrometry is presented, based on the electrostatic ion storage ring in Aarhus, ELISA. Ions with high internal energy, e.g., as a result of photoexcitation, dissociate and the yield of neutrals is monitored as a function of time. This gives information on lifetimes in the microsecond to millisecond time range but no information on the fragment masses. To determine the dissociation channels, we have introduced pulsed supplies with switching times of a few microseconds. This allows rapid switching from storage of parent ions to storage of daughter ions, which are dumped into a detector after a number of revolutions in the ring. A fragment mass spectrum is obtained by monitoring the daughter ion signal as a function of the ring voltages. This technique allows identification of the dissociation channels and determination of the time dependent competition between these channels. 0 2008 American Institute of Physics.}",
    	doi = "{10.1063/1.2884121}",
    	article-number = "{023107}",
    	issn = "{0034-6748}",
    	unique-id = "{ISI:000254194400008}"
    }
    
  67. Henning Zettergren, Manuel Alcami and Fernando Martin.
    First- and second-electron affinities of C(60) and C(70) isomers. PHYSICAL REVIEW A 76(4), October 2007.
    DOI BibTeX

    @article{ ISI:000250619700117,
    	author = "Zettergren, Henning and Alcami, Manuel and Martin, Fernando",
    	title = "{First- and second-electron affinities of C(60) and C(70) isomers}",
    	journal = "{PHYSICAL REVIEW A}",
    	year = "{2007}",
    	volume = "{76}",
    	number = "{4}",
    	month = "{OCT}",
    	abstract = "{We present density functional theory calculations of C(60)(q-) and C(70)(q-) (q=0-2) isomers that contain zero to three pairs of adjacent pentagons. The first- and second-electron affinities for the archetype structures of C(60) and C(70) are close to the experimental results, while isomers with pentagon adjacencies have significantly higher values. The results are rationalized in view of the numbers and locations of pentagon adjacencies in the fullerene cages and the spherical aromaticity for the magic number C(70)(2-) with a closed (1=5) electronic shell in the spherical gas model.}",
    	doi = "{10.1103/PhysRevA.76.043205}",
    	article-number = "{043205}",
    	issn = "{1050-2947}",
    	researcherid-numbers = "{Alcami, Manuel/F-1366-2010}",
    	unique-id = "{ISI:000250619700117}"
    }
    
  68. Henning Zettergren, Goar Sanchez, Sergio Diaz-Tendero, Manuel Alcami and Fernando Martin.
    Theoretical study of the stability of multiply charged C-70 fullerenes. JOURNAL OF CHEMICAL PHYSICS 127(10), 2007.
    DOI BibTeX

    @article{ ISI:000249474400019,
    	author = "Zettergren, Henning and Sanchez, Goar and Diaz-Tendero, Sergio and Alcami, Manuel and Martin, Fernando",
    	title = "{Theoretical study of the stability of multiply charged C-70 fullerenes}",
    	journal = "{JOURNAL OF CHEMICAL PHYSICS}",
    	year = "{2007}",
    	volume = "{127}",
    	number = "{10}",
    	month = "{SEP 14}",
    	abstract = "{We have calculated the electronic energies and optimum geometries of C-70(q+) and C-68(q+) fullerenes (q=0-14) by means of density functional theory. The ionization energies for C-70 and C-68 fullerenes increase more or less linearly as functions of charge, consistent with the previously reported behavior for C-60 and C-58 {[}S. Diaz-Tendero , J. Chem. Phys. 123, 184306 (2005)]. The dissociation energies corresponding to the C-70(q+)-> C-68(q+)+C-2, C-70(q+)-> C-68((q-1)+)+C-2(+), C-70(q+)-> C-68((q-2)+)+C++C+, C-70(q+)-> C-68((q-3)+)+C2++C+, and C-70(q+)-> C-68((q-4)+)+C2++C2+ decay channels show that C-70(q+) (like C-60(q+)) is thermodynamically unstable for q >= 6. However, the slope of the dissociation energy as a function of charge for a given decay channel is different from that of C-60(q+) fullerenes. On the basis of these results, we predict q=17 to be the highest charge state for which a fission barrier exists for C-70(q+).}",
    	doi = "{10.1063/1.2768361}",
    	article-number = "{104308}",
    	issn = "{0021-9606}",
    	researcherid-numbers = "{Alcami, Manuel/F-1366-2010}",
    	unique-id = "{ISI:000249474400019}"
    }
    
  69. S Wethekam, H Winter, H Cederquist and H Zettergren.
    Neutralization of charged fullerenes during grazing scattering from a metal surface. PHYSICAL REVIEW LETTERS 99(3), 2007.
    DOI BibTeX

    @article{ ISI:000248194700056,
    	author = "Wethekam, S. and Winter, H. and Cederquist, H. and Zettergren, H.",
    	title = "{Neutralization of charged fullerenes during grazing scattering from a metal surface}",
    	journal = "{PHYSICAL REVIEW LETTERS}",
    	year = "{2007}",
    	volume = "{99}",
    	number = "{3}",
    	month = "{JUL 20}",
    	abstract = "{The neutralization of C-60(+) and C-60(2+) fullerenes with keV energies is studied for grazing scattering from a clean and flat Al(001) surface. From the measured shifts between the angular distributions for scattered projectiles of different incident charge, we derive image-charge interaction energies, which relate to the distances of electron transfer for C-60(+) and C-60(2+). These neutralization distances are in accord with a classical over-the-barrier model taking into account the image-charge effects of the Al target and the polarization of the fullerene.}",
    	doi = "{10.1103/PhysRevLett.99.037601}",
    	article-number = "{037601}",
    	issn = "{0031-9007}",
    	unique-id = "{ISI:000248194700056}"
    }
    
  70. Henning Zettergren, Henning T Schmidt, Peter Reinhed, Henrik Cederquist, Jens Jensen, Preben Hvelplund, Shigeo Tomita, Bruno Manil, Jimmy Rangama and Bernd A Huber.
    Stabilities of multiply charged dimers and clusters of fullerenes. JOURNAL OF CHEMICAL PHYSICS 126(22), 2007.
    DOI BibTeX

    @article{ ISI:000247247400015,
    	author = "Zettergren, Henning and Schmidt, Henning T. and Reinhed, Peter and Cederquist, Henrik and Jensen, Jens and Hvelplund, Preben and Tomita, Shigeo and Manil, Bruno and Rangama, Jimmy and Huber, Bernd A.",
    	title = "{Stabilities of multiply charged dimers and clusters of fullerenes}",
    	journal = "{JOURNAL OF CHEMICAL PHYSICS}",
    	year = "{2007}",
    	volume = "{126}",
    	number = "{22}",
    	month = "{JUN 14}",
    	abstract = "{The authors find even-odd variations as functions of r (<= 7) for multiple ionization of van der Waals dimers in slow Xe(30+)+{[}C(60)](2)({[}C(60)C(70)])->center dot+{[}C(60)](2)(r+)({[}C(60)C(70)](r+)) electron-transfer collisions. This even-odd behavior is in sharp contrast to the smooth one for fullerene monomers and may be related to even-odd effects in dimer ionization energies in agreement with results from an electrostatic model. The kinetic energy releases for dimer dissociations {[}predominantly yielding intact fullerenes {[}C(60)](2)(r+)-> C(60)(r1+)+C(60)(r2+) in the same (r1=r2) or nearby (r1=r2 +/- 1) charge states] are found to be low in comparison with the corresponding model results indicating that internal excitations of the separating (intact) fullerenes are important. Experimental appearance sizes for the heavier clusters of fullerenes {[}C(60)](n)(r+) (n > 3 and r=2-5) compare well with predictions from a new nearest-neighbor model assuming that r unit charges in {[}C(60)](n)(r+) are localized to r C(60) molecules such that the Coulomb energy of the system is minimized. The system is then taken to be stable if (i) two (singly) charged C(60) are not nearest neighbors and (ii) the r C(60)(+) molecules have binding energies to their neutral nearest neighbors which are larger than the repulsive energies for the (r-1) C(60)(+)-C(60)(+) pairs. Essential ingredients in the nearest-neighbor model are cluster geometries and the present results on dimer stabilities. (c) 2007 American Institute of Physics.}",
    	doi = "{10.1063/1.2743433}",
    	article-number = "{224303}",
    	issn = "{0021-9606}",
    	unique-id = "{ISI:000247247400015}"
    }
    
  71. H Zettergren, H T Schmidt, P Reinhed, H Cederquist, J Jensen, P Hvelplund, S Tomita, B Manil, J Rangama and B A Huber.
    {Even-odd effects in the ionization cross sections of [C-60](2) and [C60C70] dimers}. PHYSICAL REVIEW A 75(5), May 2007.
    DOI BibTeX

    @article{ ISI:000246890400009,
    	author = "Zettergren, H. and Schmidt, H. T. and Reinhed, P. and Cederquist, H. and Jensen, J. and Hvelplund, P. and Tomita, S. and Manil, B. and Rangama, J. and Huber, B. A.",
    	title = "{Even-odd effects in the ionization cross sections of {[}C-60](2) and {[}C60C70] dimers}",
    	journal = "{PHYSICAL REVIEW A}",
    	year = "{2007}",
    	volume = "{75}",
    	number = "{5}",
    	month = "{MAY}",
    	abstract = "{We report strong even-odd effects in multiple ionization yields of van der Waals dimers in slow Xe30++{[}C-60](2)({[}C60C70])->center dot center dot center dot+{[}C-60](2)(r+)({[}C60C70](r+)) electron-transfer collisions as functions of r <= 7. This behavior may be due to even-odd variations in the sequences of dimer ionization energies as calculated with an electrostatic model including an electrical fullerene-fullerene contact at the 19a(0) center-center separation in {[}C-60](2)(+). Prompt dissociations predominantly yield intact fullerenes {[}C-60](2)(r+)-> C-60(1)r++C-60(2)r+ in the same (r(1)=r(2), even r) or nearby (r(1)=r(2)+/- 1, odd r>1) charge states.}",
    	doi = "{10.1103/PhysRevA.75.051201}",
    	article-number = "{051201}",
    	issn = "{1050-2947}",
    	unique-id = "{ISI:000246890400009}"
    }
    
  72. B Liu, Brondsted S Nielsen, P Hvelplund, H Zettergren, H Cederquist, B Manil and B A Huber.
    Collision-induced dissociation of hydrated adenosine monophosphate nucleotide ions: Protection of the ion in water nanoclusters. PHYSICAL REVIEW LETTERS 97(13), 2006.
    DOI BibTeX

    @article{ ISI:000240872700020,
    	author = "Liu, B. and Nielsen, S. Brondsted and Hvelplund, P. and Zettergren, H. and Cederquist, H. and Manil, B. and Huber, B. A.",
    	title = "{Collision-induced dissociation of hydrated adenosine monophosphate nucleotide ions: Protection of the ion in water nanoclusters}",
    	journal = "{PHYSICAL REVIEW LETTERS}",
    	year = "{2006}",
    	volume = "{97}",
    	number = "{13}",
    	month = "{SEP 29}",
    	abstract = "{Fragmentation of singly charged anions of adenosine 5'-monophosphate (AMP(-)) induced by collisions with neutral atoms (Ne, Na) has been studied at a collision energy of 50 keV. The experiments were performed with isolated AMP(-) as well as with AMP(-) anions nanosolvated in a cluster with a given number m of water molecules. In the first case, the dominant fragmentation channels concern the loss of adenine, PO3- and H2PO4-. In the latter, loss of water molecules becomes the dominating process, and the AMP(-) ion is fully protected when m is larger than similar to 13. The observed fragment distributions are well described with the model of an evaporative ensemble.}",
    	doi = "{10.1103/PhysRevLett.97.133401}",
    	article-number = "{133401}",
    	issn = "{0031-9007}",
    	unique-id = "{ISI:000240872700020}"
    }
    
  73. O Kamalou, B Manil, H Lebius, J Rangama, B A Huber, P Hvelplund, S Tomita, J Jensen, H T Schmidt, H Zettergren and H Cederquist.
    Fullerene collisions and clusters of fullerenes. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 252(2):117-125, 2006.
    DOI BibTeX

    @article{ ISI:000237768900006,
    	author = "Kamalou, O. and Manil, B. and Lebius, H. and Rangama, J. and Huber, B. A. and Hvelplund, P. and Tomita, S. and Jensen, J. and Schmidt, H. T. and Zettergren, H. and Cederquist, H.",
    	title = "{Fullerene collisions and clusters of fullerenes}",
    	journal = "{INTERNATIONAL JOURNAL OF MASS SPECTROMETRY}",
    	year = "{2006}",
    	volume = "{252}",
    	number = "{2}",
    	pages = "{117-125}",
    	month = "{MAY 15}",
    	abstract = "{Electron capture processes were studied in glancing collisions between multiply charged C(60)(q+) ions and neutral C(60) molecules at low collision energies where nuclear stopping dominates the interaction (typical energy: 10 keV; velocity v = 0.024 a.u.). In addition, clusters of fullerenes were multiply ionized in collisions with highly charged slow ions and their fragmentation spectra were measured by applying multi-coincidence techniques in a second, separate experiment. Through the first experiment we show that non-fragmenting electron capture collisions do not produce free electrons in C(60)(q+)-C(60) collisions (q = 1-5), i.e., the cross sections for transfer ionization processes are negligible in this charge state regime. This is in contrast to the case of atomic projectile ions where transfer ionization processes, as e.g., C(q+) + C(60) -> C((q-r)+) + C(60)(r+) -> C((q-r+1)+) + C(60)(r+) +e(-), are strong for q > 2. These results are rationalized by means of the classical over-the-barrier model for electron transfer between two C(60) molecules, or between an atomic ion and a C(60) molecule, where the molecules are modeled as conducting spheres. Further, the same model may also be used as a basis for understanding the present observations of limitations in the maximum numbers of charges, which might be transferred in non-fragmenting C(60)(q+)-C(60) collisions (q/2 for even q and (q + 1)/2 for odd q) and in C(q+)-C(60) collision (here up to q charges may be transferred). In the same experiment, we have further measured scattering angles, theta, and energy losses, epsilon, for the fullerene projectiles in C(60)(q+)-C(60) collisions and we have found low values for both theta and epsilon, which, however, increase with the number of C(2)-units lost from the projectile fullerene in electron capture collisions. The critical distances for electron transfer which are deduced from the C(60)(q+)-C(60) collision experiment and the Zettergren model are then used to explain the high charge mobility between the individual C(60) molecules in charged (C(60))(n) van der Waal's clusters of fullerenes, which we observe in the second experiment. (C) 2006 Elsevier BX All rights reserved.}",
    	doi = "{10.1016/j.ijms.2005.12.054}",
    	issn = "{1387-3806}",
    	unique-id = "{ISI:000237768900006}"
    }
    
  74. H Zettergren, P Reinhed, K Stochkel, HT Schmidt, H Cederquist, J Jensen, S Tomita, SB Nielsen, P Hvelplund, B Manil, J Rangama and BA Huber.
    Fragmentation and ionization of C-70 and C-60 by slow ions of intermediate charge. EUROPEAN PHYSICAL JOURNAL D 38(2):299-306, May 2006.
    DOI BibTeX

    @article{ ISI:000236841000009,
    	author = "Zettergren, H and Reinhed, P and Stochkel, K and Schmidt, HT and Cederquist, H and Jensen, J and Tomita, S and Nielsen, SB and Hvelplund, P and Manil, B and Rangama, J and Huber, BA",
    	title = "{Fragmentation and ionization of C-70 and C-60 by slow ions of intermediate charge}",
    	journal = "{EUROPEAN PHYSICAL JOURNAL D}",
    	year = "{2006}",
    	volume = "{38}",
    	number = "{2}",
    	pages = "{299-306}",
    	month = "{MAY}",
    	abstract = "{We have measured total and coincident (with outgoing charge-state analyzed projectiles) ionization and fragmentation spectra of C-60 and C-70 following collisions with Xe4+ and Kr4+ at v = 0.06 a.u. Intact positive fullerene ions in charge states up to five (C-60(5+) and C-70(5+)) are produced with both projectiles and for Kr4++C-70 collisions we even observe a small C-70(6+) peak. The C-60/70-2m(3+) (m=1-7) intensity distributions are predominantly associated with the stabilization of three electrons on the projectile (s=3) and are significantly different for Xe4+- and Kr4+-projectiles. On the other hand, we find remarkable similarities in the C-3(+)-C-11(+) multi-fragmentation pattern regardless of projectile species (mass) although they are associated with closer encounters in which the projectile is fully neutralized (s=4). Simple Monte Carlo calculations of nuclear and electronic loss processes show that both these contributions are very similar in glancing Xe4++C-60 and Kr4++C-60 collisions, suggesting that frontal (and more violent) collisions are strongly suppressed under the present experimental conditions. Nevertheless it is surprising that the more distant collisions (s=3) are projectile mass dependent, while the closer collisions (s=4) are not. This indicates that this simple approach (although it reproduces more advanced quantum mechanical calculations for slow collisions with singly charged atomic ions rather well) is not valid for a comprehensive description of the energy transfer processes in the present collision systems involving projectiles of higher charge states.}",
    	doi = "{10.1140/epjd/e2006-00005-7}",
    	issn = "{1434-6060}",
    	unique-id = "{ISI:000236841000009}"
    }
    
  75. D Fischer, K Stochkel, H Cederquist, H Zettergren, P Reinhed, R Schuch, A Kallberg, A Simonsson and H T Schmidt.
    Experimental separation of the Thomas charge-transfer process in high-velocity p-He collisions. PHYSICAL REVIEW A 73(5), May 2006.
    DOI BibTeX

    @article{ ISI:000237949300078,
    	author = "Fischer, D. and Stochkel, K. and Cederquist, H. and Zettergren, H. and Reinhed, P. and Schuch, R. and Kallberg, A. and Simonsson, A. and Schmidt, H. T.",
    	title = "{Experimental separation of the Thomas charge-transfer process in high-velocity p-He collisions}",
    	journal = "{PHYSICAL REVIEW A}",
    	year = "{2006}",
    	volume = "{73}",
    	number = "{5}",
    	month = "{MAY}",
    	abstract = "{We present differential cross sections of electron capture in 7.5 MeV and 12.5 MeV proton-helium collisions. Complete experimental separations of the Thomas and the kinematic single electron capture processes in the two-dimensional He+ momentum distribution in the plane perpendicular to the fast ion beam have been achieved. We compare the resulting projectile angular differential cross section with the two most recent theoretical calculations and expose significant deviations.}",
    	doi = "{10.1103/PhysRevA.73.052713}",
    	article-number = "{052713}",
    	issn = "{1050-2947}",
    	unique-id = "{ISI:000237949300078}"
    }
    
  76. S Tomita, JU Andersen, H Cederquist, B Concina, O Echt, JS Forster, K Hansen, BA Huber, P Hvelplund, J Jensen, B Liu, B Manil, L Maunoury, SB Nielsen, J Rangama, HT Schmidt and H Zettergren.
    Lifetimes of C-60(2-) and C-70(2-) dianions in a storage ring. JOURNAL OF CHEMICAL PHYSICS 124(2), 2006.
    DOI BibTeX

    @article{ ISI:000234607700027,
    	author = "Tomita, S and Andersen, JU and Cederquist, H and Concina, B and Echt, O and Forster, JS and Hansen, K and Huber, BA and Hvelplund, P and Jensen, J and Liu, B and Manil, B and Maunoury, L and Nielsen, SB and Rangama, J and Schmidt, HT and Zettergren, H",
    	title = "{Lifetimes of C-60(2-) and C-70(2-) dianions in a storage ring}",
    	journal = "{JOURNAL OF CHEMICAL PHYSICS}",
    	year = "{2006}",
    	volume = "{124}",
    	number = "{2}",
    	month = "{JAN 14}",
    	abstract = "{C-60(2-) and C-70(2-) dianions have been produced by electrospray of the monoanions and subsequent electron pickup in a Na vapor cell. The dianions were stored in an electrostatic ring and their decay by electron emission was measured up to 1 s after injection. While C-70(2-) ions are stable on this time scale, except for a small fraction of the ions which have been excited by gas collisions, most of the C-60(2-) ions decay on a millisecond time scale, with a lifetime depending strongly on their internal temperature. The results can be modeled as decay by electron tunneling through a Coulomb barrier, mainly from thermally populated triplet states about 120 meV above a singlet ground state. At times longer than about 100 ms, the absorption of blackbody radiation plays an important role for the decay of initially cold ions. The tunneling rates obtained from the modeling, combined with WKB estimates of the barrier penetration, give a ground-state energy 200 +/- 30 meV above the energy of the monoanion plus a free electron and a ground-state lifetime of the order of 20 s. (c) 2006 American Institute of Physics.}",
    	doi = "{10.1063/1.2155435}",
    	article-number = "{024310}",
    	issn = "{0021-9606}",
    	researcherid-numbers = "{Hansen, Klavs/J-1959-2012}",
    	unique-id = "{ISI:000234607700027}"
    }
    
  77. K Stochkel, O Eidem, H Cederquist, H Zettergren, P Reinhed, R Schuch, CL Cocke, SB Levin, VN Ostrovsky, A Kalberg, A Simonsson, J Jensen and HT Schmidt.
    Two-center interference in fast proton-H-2-electron transfer and excitation processes. PHYSICAL REVIEW A 72(5), November 2005.
    DOI BibTeX

    @article{ ISI:000233603400010,
    	author = "Stochkel, K and Eidem, O and Cederquist, H and Zettergren, H and Reinhed, P and Schuch, R and Cocke, CL and Levin, SB and Ostrovsky, VN and Kalberg, A and Simonsson, A and Jensen, J and Schmidt, HT",
    	title = "{Two-center interference in fast proton-H-2-electron transfer and excitation processes}",
    	journal = "{PHYSICAL REVIEW A}",
    	year = "{2005}",
    	volume = "{72}",
    	number = "{5}",
    	month = "{NOV}",
    	abstract = "{We present experimental evidence for a strong dependence on the angle between the molecular axis of H-2 and the direction of the incoming projectile (p) in the cross section for transfer excitation in fast p-H-2 collisions. For collision energies of 1.0 and 1.3 MeV we find good agreement between the observed data and an analytical expression based on a two-atomic-center description using Brinkman-Kramers amplitudes. This clearly shows that the observed angular dependence is a result of quantum mechanical interference and not a trivial geometrical effect.}",
    	doi = "{10.1103/PhysRevA.72.050703}",
    	article-number = "{050703}",
    	issn = "{1050-2947}",
    	unique-id = "{ISI:000233603400010}"
    }
    
  78. B Manil, L Maunoury, J Jensen, H Cederquist, HT Schmidt, H Zettergren, P Hvelplund, S Tomita and BA Huber.
    Fragmentation of charged fullerene dimers: Kinetic energy release. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 235:419-424, July 2005.
    DOI BibTeX

    @article{ ISI:000230334400084,
    	author = "Manil, B and Maunoury, L and Jensen, J and Cederquist, H and Schmidt, HT and Zettergren, H and Hvelplund, P and Tomita, S and Huber, BA",
    	title = "{Fragmentation of charged fullerene dimers: Kinetic energy release}",
    	journal = "{NUCLEAR INSTRUMENTS \& METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS}",
    	year = "{2005}",
    	volume = "{235}",
    	pages = "{419-424}",
    	month = "{JUL}",
    	note = "{12th International Conference on the Physics of Highly Charged Ions, Vilnius, LITHUANIA, SEP 06-11, 2004}",
    	abstract = "{We have performed an experimental study of highly charged clusters of fullerenes produced in slow collisions with highly charged ions. Collision products are analysed with respect to their mass to charge ratio and their initial kinectic energy by a linear time-of-flight mass spectrometer. An event-by-event data registration mode allows to study the correlation between the different detected fragments. In this paper, we focus on the kinetic energy releases (KER) in the fragmentation of charged dimers of fullerenes. The results are compared with theoretical values obtained from the conducting sphere model. (c) 2005 Elsevier B.V. All rights reserved.}",
    	doi = "{10.1016/j.nimb.2005.03.217}",
    	issn = "{0168-583X}",
    	unique-id = "{ISI:000230334400084}"
    }
    
  79. HT Schmidt, J Jensen, P Reinhed, R Schuch, K Stochkel, H Zettergren, H Cederquist, L Bagge, H Danared, A Kallberg, H Schmidt-Bocking and CL Cocke.
    Recoil-ion momentum distributions for transfer ionization in fast proton-He collisions. PHYSICAL REVIEW A 72(1), July 2005.
    DOI BibTeX

    @article{ ISI:000230887300093,
    	author = "Schmidt, HT and Jensen, J and Reinhed, P and Schuch, R and Stochkel, K and Zettergren, H and Cederquist, H and Bagge, L and Danared, H and Kallberg, A and Schmidt-Bocking, H and Cocke, CL",
    	title = "{Recoil-ion momentum distributions for transfer ionization in fast proton-He collisions}",
    	journal = "{PHYSICAL REVIEW A}",
    	year = "{2005}",
    	volume = "{72}",
    	number = "{1}",
    	month = "{JUL}",
    	abstract = "{We present high-luminosity experimental investigations of the transfer ionization (TI:p+He -> H-0+He2++e(-)) process in collisions between fast protons and neutral helium atoms in the earlier inaccessibly high-energy range 1.4-5.8 MeV. The protons were stored in the heavy-ion storage and cooler ring CRYRING, where they intersected a narrow supersonic helium gas jet. We discuss the longitudinal recoil-ion momentum distribution, as measured by means of cold-target recoil-ion momentum spectroscopy and find that this distribution splits into two completely separated peaks at the high end of our energy range. These separate contributions are discussed in terms of the earlier proposed Thomas TI (TTI) and kinematic TI mechansims. The cross section of the TTI process is found to follow a sigma proportional to v(-b) dependence with b=10.78 +/- 0.27 in accordance with the expected v(-11) asymptotic behavior. Further, we discuss the probability for shake-off accompanying electron transfer and the relation of this TI mechanism to photodouble ionization. Finally the influence of the initial-state electron velocity distribution on the TTI process is discussed.}",
    	doi = "{10.1103/PhysRevA.72.012713}",
    	article-number = "{012713}",
    	issn = "{1050-2947}",
    	unique-id = "{ISI:000230887300093}"
    }
    
  80. HT Schmidt, A Fardi, J Jensen, P Reinhed, R Schuch, K Stochkel, H Zettergren, H Cederquist and CL Cocke.
    Transfer ionization in p+He collisions. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 233:43-47, May 2005.
    DOI BibTeX

    @article{ ISI:000230063600008,
    	author = "Schmidt, HT and Fardi, A and Jensen, J and Reinhed, P and Schuch, R and Stochkel, K and Zettergren, H and Cederquist, H and Cocke, CL",
    	title = "{Transfer ionization in p+He collisions}",
    	journal = "{NUCLEAR INSTRUMENTS \& METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS}",
    	year = "{2005}",
    	volume = "{233}",
    	pages = "{43-47}",
    	month = "{MAY}",
    	note = "{8th Workshop on Fast Ion-Atom Collisions, Debrecen, HUNGARY, SEP 01-03, 2004}",
    	abstract = "{Using the unique combination of the high-quality ion beams available in the heavy-ion storage ring CRYRING at the Manne Siegbahn Laboratory, Stockholm and our COLTRIMS (cold target recoil-ion-momentum spectroscopy) setup with a pulsed extraction system we have investigated the recoil-ion-momentum distributions for transfer ionization in p-He collisions at energies up to 5.8 MeV. This technique allows us to determine the separate contribution to the cross section from the Thomas p-e-e scattering mechanism. Unlike the situation at lower collision energies we find that the cross section follows the expected asymptotic v(-11) scaling. (c) 2005 Published by Elsevier B.V.}",
    	doi = "{10.1016/j.nimb.2005.03.084}",
    	issn = "{0168-583X}",
    	unique-id = "{ISI:000230063600008}"
    }
    
  81. L Maunoury, B Manil, J Rangama, H Lebius, BA Huber, JY Pacquet, R Leroy, UV Pedersen, P Hvelplund, J Jensen, S Tomita, H Zettergren, HT Schmidt, H Cederquist and F Gustavo.
    Ion beams of carbon clusters and multiply charged fullerenes produced with electron cyclotron resonance ion sources. REVIEW OF SCIENTIFIC INSTRUMENTS 76(5), May 2005.
    DOI BibTeX

    @article{ ISI:000229064300015,
    	author = "Maunoury, L and Manil, B and Rangama, J and Lebius, H and Huber, BA and Pacquet, JY and Leroy, R and Pedersen, UV and Hvelplund, P and Jensen, J and Tomita, S and Zettergren, H and Schmidt, HT and Cederquist, H and Gustavo, F",
    	title = "{Ion beams of carbon clusters and multiply charged fullerenes produced with electron cyclotron resonance ion sources}",
    	journal = "{REVIEW OF SCIENTIFIC INSTRUMENTS}",
    	year = "{2005}",
    	volume = "{76}",
    	number = "{5}",
    	month = "{MAY}",
    	abstract = "{The production of carbon cluster ions by injecting C-60 fullerene vapor into different electron cyclotron resonance (ECR) ion sources (MONO1001/2.45 GHz and CAPRICE/14 GHz) is described. The extracted ion mass spectra show a bimodal distribution, well known from collisions between electrons or ions and fullerenes. In addition to small carbon clusters and even-numbered fullerene ions, odd-numbered clusters with (n > 30) are detected with low intensities. In particular, we have analyzed the mass spectra as a function of the rf power applied to the ECR plasma. Optimum power values are found for the production of individual carbon cluster ions, which increase with decreasing cluster size. Whereas at low power the production of fullerene ions dominates, the intensity of the very small carbon clusters is found to strongly increase with the injected power. This difference in the power dependence is used to vary and to determine the beam composition for ions with identical mass/charge ratios. (c) 2005 American Institute of Physics.}",
    	doi = "{10.1063/1.1900663}",
    	article-number = "{053304}",
    	issn = "{0034-6748}",
    	unique-id = "{ISI:000229064300015}"
    }
    
  82. JU Andersen, H Cederquist, JS Forster, BA Huber, P Hvelplund, J Jensen, B Liu, B Manil, L Maunoury, SB Nielsen, UV Pedersen, J Rangama, HT Schmidt, S Tomita and H Zettergren.
    Photodissociation of protonated amino acids and peptides in an ion storage ring. Determination of Arrhenius parameters in the high-temperature limit. PHYSICAL CHEMISTRY CHEMICAL PHYSICS 6(10):2676-2681, 2004.
    DOI BibTeX

    @article{ ISI:000222182100018,
    	author = "Andersen, JU and Cederquist, H and Forster, JS and Huber, BA and Hvelplund, P and Jensen, J and Liu, B and Manil, B and Maunoury, L and Nielsen, SB and Pedersen, UV and Rangama, J and Schmidt, HT and Tomita, S and Zettergren, H",
    	title = "{Photodissociation of protonated amino acids and peptides in an ion storage ring. Determination of Arrhenius parameters in the high-temperature limit}",
    	journal = "{PHYSICAL CHEMISTRY CHEMICAL PHYSICS}",
    	year = "{2004}",
    	volume = "{6}",
    	number = "{10}",
    	pages = "{2676-2681}",
    	month = "{MAY 21}",
    	abstract = "{We have measured the time dependence of the fragmentation of protonated amino acids and peptides upon UV excitation in an electrostatic ion storage ring. After absorption of a 266 nm photon, protonated Trp (TrpH(+)) has a lifetime of 10-20 mus but also a component with a millisecond lifetime is present. The long lifetime may be due to fluorescence, which leads to ions with lower excitation energy, or to the decay of the Trp(+.) radical cation formed after prompt hydrogen loss in the laser interaction region. Only one component with a lifetime of about 10 mus was detected for TyrH(+). The lifetime of photoexcited PheH(+) is even shorter with an upper limit of a few microseconds. For the singly protonated tripeptides (LysTrpLysH(+) and LysTyrLysH(+)), the decay curves are found to consist of a single component that can be reproduced with an assumption of statistical decay after equilibration of the photon energy among all vibrational modes. The rate constant is expressed in the Arrhenius form in terms of the microcanonical temperature, and the decay rate is obtained by integration over the energy distribution, which has a spread corresponding to the canonical energy distribution at room temperature. The resulting deviation from exponential decay makes it possible to determine the decay parameters from a measurement at a single photon wavelength. Activation energies of E(a), 1.24 +/- 0.07 and 1.5 +/- 0.4 eV were determined for LysTrpLysH(+) and LysTyrLysH(+), respectively, with pre-exponential factors of A(d) = 10(11.1+/-0.5) and 10(12.9+/-2.6) s(-1).}",
    	doi = "{10.1039/b316845j}",
    	issn = "{1463-9076}",
    	unique-id = "{ISI:000222182100018}"
    }
    
  83. J Jensen, H Zettergren, HT Schmidt, H Cederquist, S Tomita, SB Nielsen, J Rangama, P Hvelplund, B Manil and BA Huber.
    Ionization of C-70 and C-60 molecules by slow highly charged ions: A comparison. PHYSICAL REVIEW A 69(5), May 2004.
    DOI BibTeX

    @article{ ISI:000221813700102,
    	author = "Jensen, J and Zettergren, H and Schmidt, HT and Cederquist, H and Tomita, S and Nielsen, SB and Rangama, J and Hvelplund, P and Manil, B and Huber, BA",
    	title = "{Ionization of C-70 and C-60 molecules by slow highly charged ions: A comparison}",
    	journal = "{PHYSICAL REVIEW A}",
    	year = "{2004}",
    	volume = "{69}",
    	number = "{5}",
    	month = "{MAY}",
    	abstract = "{We have studied collisions between slow highly charged ions and pure C-70 and C-60 molecular targets, and report on measurements of target ionization and fragmentation in electron transfer processes. The intensity distributions in the fragmentation spectra for C-60 and C-70 are rather similar, indicating that similar roles are played by evaporation (neutral C-2 emission) and fission processes (charged particle emission) in the two systems. For C-70, intact molecular ions are formed in charge states up to 10+, while the maximum charge state for C-60 molecules is 9+ following collisions with Xe23+ at 69 keV. The kinetic-energy releases measured for asymmetric fission of C-70 ions (C-70(r+)-->C-68((r-1))+C-2(+)) are mostly close to the corresponding ones for C-60, while both sets of results are significantly lower than those reported for electron-impact ionization studies of C-60 and C-70. Kinetic-energy releases and fission barrier heights are estimated for C-60 and C-70 ions using an electrostatic model. An increased intensity of the higher charge states of C-70 ions is observed compared to the C-60 case, which most likely is due to a larger number of degrees of freedom on which the internal excitation energy may be distributed.}",
    	doi = "{10.1103/PhysRevA.69.053203}",
    	article-number = "{053203}",
    	issn = "{1050-2947}",
    	unique-id = "{ISI:000221813700102}"
    }
    
  84. H Zettergren, J Jensen, HT Schmidt and H Cederquist.
    Electrostatic model calculations of fission barriers for fullerene ions. EUROPEAN PHYSICAL JOURNAL D 29(1):63-68, April 2004.
    DOI BibTeX

    @article{ ISI:000221058100010,
    	author = "Zettergren, H and Jensen, J and Schmidt, HT and Cederquist, H",
    	title = "{Electrostatic model calculations of fission barriers for fullerene ions}",
    	journal = "{EUROPEAN PHYSICAL JOURNAL D}",
    	year = "{2004}",
    	volume = "{29}",
    	number = "{1}",
    	pages = "{63-68}",
    	month = "{APR}",
    	abstract = "{We present model calculations of kinetic energy releases and fission barriers in asymmetric fission of C-60(r+) ions, using a simple electrostatic model where the fragments are treated as conducting spheres. The kinetic energy releases are calculated using two different approaches for deducing the radii of the spheres. Both approaches give results in qualitative agreement with experimental results. The fission barriers, oil the other hand, depend strongly on the model radii and the activation energies for neutral fragment emission. A comparison between the model calculations shows that the choice of the finite size of the smaller fragments become important as r increases and have large influences on the prediction for the C-60(r+) stability limit. The competition between neutral (evaporation) and charged-fragment emission (fission) are discussed within a static over-the-barrier model for electron transfer between conducting spheres.}",
    	doi = "{10.1140/epjd/e2004-00006-6}",
    	issn = "{1434-6060}",
    	unique-id = "{ISI:000221058100010}"
    }
    
  85. B Manil, L Maunoury, BA Huber, J Jensen, HT Schmidt, H Zettergren, H Cederquist, S Tomita and P Hvelplund.
    Highly charged clusters of fullerenes: Charge mobility and appearance sizes. PHYSICAL REVIEW LETTERS 91(21), 2003.
    DOI BibTeX

    @article{ ISI:000186757000035,
    	author = "Manil, B and Maunoury, L and Huber, BA and Jensen, J and Schmidt, HT and Zettergren, H and Cederquist, H and Tomita, S and Hvelplund, P",
    	title = "{Highly charged clusters of fullerenes: Charge mobility and appearance sizes}",
    	journal = "{PHYSICAL REVIEW LETTERS}",
    	year = "{2003}",
    	volume = "{91}",
    	number = "{21}",
    	month = "{NOV 21}",
    	abstract = "{Clusters of fullerenes (C-60,C-70)(n) are produced in a gas aggregation source and are multiply ionized in collisions with highly charged Xe-20+,Xe-30+ ions. Their stabilities and decay processes are analyzed with high-resolution time-of-flight mass spectrometry. Fullerene clusters in charge states up to q=5 have been observed and appearance sizes are found to be as small as n(app)=5, 10, 21, and 33 for q=2, 3, 4, and 5, respectively. The analysis of the multicoincident fragmentation spectra indicates a high charge mobility. This is in contrast to charge localization effects which have been reported for Ar-n(q+) rare gas clusters. Clusters of fullerenes are found to be conducting when multiply charged.}",
    	doi = "{10.1103/PhysRevLett.91.215504}",
    	article-number = "{215504}",
    	issn = "{0031-9007}",
    	unique-id = "{ISI:000186757000035}"
    }
    
  86. JU Andersen, H Cederquist, JS Forster, BA Huber, P Hvelplund, J Jensen, B Liu, B Manil, L Maunoury, SB Nielsen, UV Pedersen, HT Schmidt, S Tomita and H Zettergren.
    Power-law decay of collisionally excited amino acids and quenching by radiative cooling. EUROPEAN PHYSICAL JOURNAL D 25(2):139-148, August 2003.
    DOI BibTeX

    @article{ ISI:000184935300005,
    	author = "Andersen, JU and Cederquist, H and Forster, JS and Huber, BA and Hvelplund, P and Jensen, J and Liu, B and Manil, B and Maunoury, L and Nielsen, SB and Pedersen, UV and Schmidt, HT and Tomita, S and Zettergren, H",
    	title = "{Power-law decay of collisionally excited amino acids and quenching by radiative cooling}",
    	journal = "{EUROPEAN PHYSICAL JOURNAL D}",
    	year = "{2003}",
    	volume = "{25}",
    	number = "{2}",
    	pages = "{139-148}",
    	month = "{AUG}",
    	abstract = "{We have investigated the time dependence of the fragmentation of protonated amino acids stored at 22 keV in the electrostatic ring ELISA. The ions were produced in an electrospray source and after bunching in a quadrupole trap they were excited by collisions in a Ne gas. As in earlier studies of metal clusters and fullerenes produced in ``hot{''} ion sources we find that the dissociation of metastable molecules follows approximately a 1/t decay law until a time tau after which the yield falls off much more rapidly. We interpret this reduction as a result of radiative cooling with a characteristic cooling time, tau(c) similar or equal to G(T), where G is the magnitude of the exponent in an Arrhenius expression for the rate of the dominant fragmentation process. The values of tau obtained from fits to the data are in the range 9-17 ms corresponding to cooling times of a few hundred milliseconds, in good accord with the expected rate of cooling by emission from IR-active vibrations. The power-law behaviour for t < tau varies somewhat between the different amino acids, with powers between -0.9 and -1.1. We argue that this may be due to a competition between fragmentation channels with different Arrhenius parameters.}",
    	doi = "{10.1140/epjd/e2003-00093-9}",
    	issn = "{1434-6060}",
    	unique-id = "{ISI:000184935300005}"
    }
    
  87. H Cederquist, J Jensen, HT Schmidt, H Zettergren, S Tomita, BA Huber and B Manil.
    Barriers for asymmetric fission of multiply charged C-60 fullerenes. PHYSICAL REVIEW A 67(6), June 2003.
    DOI BibTeX

    @article{ ISI:000183915200077,
    	author = "Cederquist, H and Jensen, J and Schmidt, HT and Zettergren, H and Tomita, S and Huber, BA and Manil, B",
    	title = "{Barriers for asymmetric fission of multiply charged C-60 fullerenes}",
    	journal = "{PHYSICAL REVIEW A}",
    	year = "{2003}",
    	volume = "{67}",
    	number = "{6}",
    	month = "{JUN}",
    	abstract = "{We have measured kinetic energy releases in asymmetric fission, C-60(r+)-->C-58((r-1)+)+C-2(+) (r=6-9) and evaporation C-60(r+)-->C-58(r+)+C-2 (r=2,3), following multiple-electron removal from C-60 in He2+ and Xe17+ collisions at 3q keV (q=2,17). We used the recoil-ion momentum technique and limited the initial momentum distribution of the target molecules by collimation of the effusive C-60 jet. This yielded a resolution of 3 meV for the final kinetic energies of the charged C-58 fragments, mapped out as two-dimensional position distributions at the end of a linear time-of-flight mass spectrometer. The present results for asymmetric fission are in agreement with earlier ones deduced from time-of-flight C-2(+) peak-shape and sector-field C-58((r-1)+)-energy analysis. Model calculations treating C-58((r-1)+) and C-2(+) as conducting spheres indicate that the autocharge-transfer process, which has been proposed to link asymmetric fission to neutral C-2 emission, most likely is inactive for all r. Using a charge-independent activation energy for C-2 emission from C-60(r+) of E-a=10 eV, we deduce fission barriers indicating lower (semiempirical) and upper (model) C-60(r+)-stability limits of r=11 and r=18, respectively.}",
    	doi = "{10.1103/PhysRevA.67.062719}",
    	article-number = "{062719}",
    	issn = "{1050-2947}",
    	unique-id = "{ISI:000183915200077}"
    }
    
  88. J Jensen, H Zettergren, A Fardi, HT Schmidt and H Cederquist.
    Energy releases in the fission of multiply charged C-60 ions. NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 205:643-650, May 2003.
    DOI BibTeX

    @article{ ISI:000183211200125,
    	author = "Jensen, J and Zettergren, H and Fardi, A and Schmidt, HT and Cederquist, H",
    	title = "{Energy releases in the fission of multiply charged C-60 ions}",
    	journal = "{NUCLEAR INSTRUMENTS \& METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS}",
    	year = "{2003}",
    	volume = "{205}",
    	pages = "{643-650}",
    	month = "{MAY}",
    	note = "{11th International Conference on the Physics of Highly Charged Ions (HCI 2002), CAEN, FRANCE, SEP 01-06, 2002}",
    	abstract = "{We have studied electron-transfer and collision-induced fragmentation processes in collisions between slow highly charged ions and C-60 molecules. By using a position sensitive detector, located after a time-of-flight spectrometer, we obtain recoil energies of fragments resulting from post-collisional disintegration of multiply charged C-60 ions. We deduce kinetic energy releases (KERs) for the cases in which multiply charged C-60 ions emit either a single C-2(+) ion or a neutral C-2-unit. We find that C-58(4+) ions predominately are due to the emission of a neutral C-2 molecule. Model calculations of KER-values resulting from C-60(r+) ions emitting a C-2(+) ion are presented, and compared with the corresponding experimental results for C-60(r+) with 5 less than or equal to r less than or equal to 9 (C) 2003 Elsevier Science B.V. All rights reserved.}",
    	doi = "{10.1016/S0168-583X(03)00532-9}",
    	issn = "{0168-583X}",
    	unique-id = "{ISI:000183211200125}"
    }
    
  89. P Hvelplund, B Liu, SB Nielsen, S Tomita, H Cederquist, J Jensen, HT Schmidt and H Zettergren.
    Electron capture and loss by protonated peptides and proteins in collisions with C-60 and Na. EUROPEAN PHYSICAL JOURNAL D 22(1):75-79, January 2003.
    DOI BibTeX

    @article{ ISI:000180850000009,
    	author = "Hvelplund, P and Liu, B and Nielsen, SB and Tomita, S and Cederquist, H and Jensen, J and Schmidt, HT and Zettergren, H",
    	title = "{Electron capture and loss by protonated peptides and proteins in collisions with C-60 and Na}",
    	journal = "{EUROPEAN PHYSICAL JOURNAL D}",
    	year = "{2003}",
    	volume = "{22}",
    	number = "{1}",
    	pages = "{75-79}",
    	month = "{JAN}",
    	abstract = "{Electron capture and loss cross-sections have been measured for collisions between fast multiply charged peptide and protein ions {[}M+nH](n+) and Na or C-60. The ions were produced in an electrospray ion source (ESI) and accelerated to an energy of n x 50 keV. We find that the size of the cross-sections depend strongly on molecule size, ionization energy and projectile charge state n. For multiply charged ubiquitin projectiles, the cross-sections for electron capture are found to be several times larger With a Na target than with a C-60 target. This observation is qualitatively explained by means of an over-the-barrier model for electron transfer using metal-sphere descriptions for the electronic responses of the collision partners.}",
    	doi = "{10.1140/epjd/e2002-00220-2}",
    	issn = "{1434-6060}",
    	unique-id = "{ISI:000180850000009}"
    }
    
  90. HT Schmidt, A Fardi, R Schuch, SH Schwartz, H Zettergren, H Cederquist, L Bagge, H Danared, A Kallberg, J Jensen, KG Rensfelt, V Mergel, L Schmidt, H Schmidt-Bocking and CL Cocke.
    Double-to-single target ionization ratio for electron capture in fast p-He collisions. PHYSICAL REVIEW LETTERS 89(16), 2002.
    DOI BibTeX

    @article{ ISI:000178384300010,
    	author = "Schmidt, HT and Fardi, A and Schuch, R and Schwartz, SH and Zettergren, H and Cederquist, H and Bagge, L and Danared, H and Kallberg, A and Jensen, J and Rensfelt, KG and Mergel, V and Schmidt, L and Schmidt-Bocking, H and Cocke, CL",
    	title = "{Double-to-single target ionization ratio for electron capture in fast p-He collisions}",
    	journal = "{PHYSICAL REVIEW LETTERS}",
    	year = "{2002}",
    	volume = "{89}",
    	number = "{16}",
    	month = "{OCT 14}",
    	abstract = "{We have used the ion storage ring CRYRING and its internal gas-jet target and recoil-ion-momentum spectrometer to measure absolute cross sections for transfer ionization (TI: p+He-->H-0+He2++e(-)) in 2.5-4.5 MeV p-He collisions with separate Thomas (TTI) and kinematic (KTI) TI contributions. The probability for electron emission in kinematical capture decreases with increasing velocity and appears to approach the photoionization shakeoff value (1.63\%) {[}T. Aberg, Phys. Rev. A 2, 1726 (1970)]. The velocity dependence of the TTI cross section is consistent with the theoretically predicted v(-11) scaling {[}J. S. Briggs and K. Taulbjerg, J. Phys. B 12, 2565 (1979)].}",
    	doi = "{10.1103/PhysRevLett.89.163201}",
    	article-number = "{163201}",
    	issn = "{0031-9007}",
    	unique-id = "{ISI:000178384300010}"
    }
    
  91. H Zettergren, HT Schmidt, H Cederquist, J Jensen, S Tomita, P Hvelplund, H Lebius and BA Huber.
    Static over-the-barrier model for electron transfer between metallic spherical objects. PHYSICAL REVIEW A 66(3), September 2002.
    DOI BibTeX

    @article{ ISI:000178382500069,
    	author = "Zettergren, H and Schmidt, HT and Cederquist, H and Jensen, J and Tomita, S and Hvelplund, P and Lebius, H and Huber, BA",
    	title = "{Static over-the-barrier model for electron transfer between metallic spherical objects}",
    	journal = "{PHYSICAL REVIEW A}",
    	year = "{2002}",
    	volume = "{66}",
    	number = "{3}",
    	month = "{SEP}",
    	abstract = "{We present a static classical over-the-barrier model (OBM) for electron transfer between two isolated, infinitely conducting spheres with arbitrary and different electrical charges. This model is shown to be very useful for first estimates of single- and multiple-electron transfer cross sections in cluster-cluster collisions when the collision velocities are significantly lower than the typical target electron velocities. For faster collisions, more advanced models such as the dynamical OBM, or the time-dependent local density approximation (TDLDA) or the solutions of their semiclassical counterparts-the Vlasov equations have to be used. The latter two methods clearly provide the most detailed information on the electronic response, but they are also computationally very demanding and have, so far, only been used for collisions involving one cluster (and an atomic ion). We compare our static OBM results (in the limit in which one of the sphere radii approaches zero) with TDLDA and Vlasov calculations of cluster charging in Ar8+-Na-40 collisions at different velocities to demonstrate that the present static OBM is valid at sufficiently low velocities. The static OBM is then used in a comparison with experimental target charge state distributions in C-60(q+)-C-60 and Cq+-C-60 collisions at 0.01rootq and 0.06rootq v(0), respectively. Calculated electronic excitation of the projectile after two-electron transfer in C-60(4+)-C-60 collisions readily explains the recently observed suppression of the transfer ionization channel in this reaction. Finally, we model the total projectile electron loss and dissociation cross section in highly protonated Lysozyme-oxygen (Lys-H-9(9+)-O-2) collisions and make comparisons with recent experimental results at 0.01 v(0).}",
    	doi = "{10.1103/PhysRevA.66.032710}",
    	article-number = "{032710}",
    	issn = "{1050-2947}",
    	unique-id = "{ISI:000178382500069}"
    }
    
  92. A Langereis, J Jensen, A Fardi, K Haghighat, H T Schmidt, S H Schwartz, H Zettergren and H Cederquist.
    Stabilization of electrons on Ar^q+ ions after slow collisions with C60. Phys. Rev. A 63:062725, May 2001.
    URL, DOI BibTeX

    @article{PhysRevA.63.062725,
    	title = "Stabilization of electrons on Ar^q+ ions after slow collisions with C60",
    	author = "Langereis, A. and Jensen, J. and Fardi, A. and Haghighat, K. and Schmidt, H. T. and Schwartz, S. H. and Zettergren, H. and Cederquist, H.",
    	journal = "Phys. Rev. A",
    	volume = 63,
    	issue = 6,
    	pages = 062725,
    	numpages = 7,
    	year = 2001,
    	month = "May",
    	doi = "10.1103/PhysRevA.63.062725",
    	url = "http://link.aps.org/doi/10.1103/PhysRevA.63.062725",
    	publisher = "American Physical Society"
    }