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Title: Absolute cross sections for the dissociation of hydrogen cluster ions in high-energy collisions with helium atoms

Abstract

Absolute dissociation cross sections are reported for H{sub n}{sup +} clusters of varied mass (n=3,5,...,35) following collisions with He atoms at 60 keV/amu. Initial results have been published previously for a smaller range of cluster sizes [Ouaskit et al., Phys. Rev. A 49, 1484 (1994)]. The present extended study includes further experimental results, reducing the statistical errors associated with the absolute cross sections. The previously suggested quasilinear dependence of the H{sub n}{sup +} dissociation cross sections upon n is developed with reference to expected series of geometrical shells of H{sub 2} molecules surrounding a H{sub 3}{sup +} core. Recent calculations identify n=9 as corresponding to the first closed H{sub 2} shell [e.g., Stich et al., J. Chem. Phys. 107, 9482 (1997)]. Recurrence of the distinct characteristics observed in the dissociation-cross-section dependence upon cluster size around n=9 provides the basis for the presently proposed subsequent closed shells at n=15, 21, 27, and 33, in agreement with the calculations of Nagashima et al. [J. Phys. Chem. 96, 4294 (1992)].

Authors:
; ; ; ; ; ; ;  [1];  [2]
  1. Institut de Physique Nucleaire de Lyon, IN2P3-CNRS et Universite Claude Bernard Lyon 1, 43, boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex (France)
  2. (Austria)
Publication Date:
OSTI Identifier:
20974596
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. A; Journal Volume: 73; Journal Issue: 2; Other Information: DOI: 10.1103/PhysRevA.73.023201; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ATOMIC CLUSTERS; ATOMS; CROSS SECTIONS; DISSOCIATION; HELIUM; HYDROGEN IONS 3 PLUS; ION PAIRS; ION-ATOM COLLISIONS; KEV RANGE; MOLECULES; SHELLS

Citation Formats

Eden, S., Tabet, J., Samraoui, K., Louc, S., Farizon, B., Farizon, M., Ouaskit, S., Maerk, T. D., and Institut fuer Ionenphysik, Leopold Franzens Universitaet, Technikerstrasse 25, A-6020 Innsbruck. Absolute cross sections for the dissociation of hydrogen cluster ions in high-energy collisions with helium atoms. United States: N. p., 2006. Web. doi:10.1103/PHYSREVA.73.023201.
Eden, S., Tabet, J., Samraoui, K., Louc, S., Farizon, B., Farizon, M., Ouaskit, S., Maerk, T. D., & Institut fuer Ionenphysik, Leopold Franzens Universitaet, Technikerstrasse 25, A-6020 Innsbruck. Absolute cross sections for the dissociation of hydrogen cluster ions in high-energy collisions with helium atoms. United States. doi:10.1103/PHYSREVA.73.023201.
Eden, S., Tabet, J., Samraoui, K., Louc, S., Farizon, B., Farizon, M., Ouaskit, S., Maerk, T. D., and Institut fuer Ionenphysik, Leopold Franzens Universitaet, Technikerstrasse 25, A-6020 Innsbruck. Wed . "Absolute cross sections for the dissociation of hydrogen cluster ions in high-energy collisions with helium atoms". United States. doi:10.1103/PHYSREVA.73.023201.
@article{osti_20974596,
title = {Absolute cross sections for the dissociation of hydrogen cluster ions in high-energy collisions with helium atoms},
author = {Eden, S. and Tabet, J. and Samraoui, K. and Louc, S. and Farizon, B. and Farizon, M. and Ouaskit, S. and Maerk, T. D. and Institut fuer Ionenphysik, Leopold Franzens Universitaet, Technikerstrasse 25, A-6020 Innsbruck},
abstractNote = {Absolute dissociation cross sections are reported for H{sub n}{sup +} clusters of varied mass (n=3,5,...,35) following collisions with He atoms at 60 keV/amu. Initial results have been published previously for a smaller range of cluster sizes [Ouaskit et al., Phys. Rev. A 49, 1484 (1994)]. The present extended study includes further experimental results, reducing the statistical errors associated with the absolute cross sections. The previously suggested quasilinear dependence of the H{sub n}{sup +} dissociation cross sections upon n is developed with reference to expected series of geometrical shells of H{sub 2} molecules surrounding a H{sub 3}{sup +} core. Recent calculations identify n=9 as corresponding to the first closed H{sub 2} shell [e.g., Stich et al., J. Chem. Phys. 107, 9482 (1997)]. Recurrence of the distinct characteristics observed in the dissociation-cross-section dependence upon cluster size around n=9 provides the basis for the presently proposed subsequent closed shells at n=15, 21, 27, and 33, in agreement with the calculations of Nagashima et al. [J. Phys. Chem. 96, 4294 (1992)].},
doi = {10.1103/PHYSREVA.73.023201},
journal = {Physical Review. A},
number = 2,
volume = 73,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 2006},
month = {Wed Feb 15 00:00:00 EST 2006}
}
  • Single, double, triple, and quadruple ionization cross sections of small cationic carbon clusters C{sub n}{sup +} colliding with helium atoms at a fixed velocity (2.6 atomic units) have been measured. The size ranges from n=1 to n=10 for single to triple ionization, from n=5 to n=10 for the quadruple ionization. The dependence of the cross sections with the cluster size is found to be well reproduced by predictions of the independent atom and electron (IAE) collision model. This extends the applicability of this simple model to higher n values and to a higher ionization degree than previously done [M. Chabotmore » et al., Eur. Phys. J. D 14, 5 (2001)]. The branching ratios of multiply charged C{sub n}{sup q+} clusters remaining intact over a 100 ns time window have been measured (n=3-10, q=2-3). Branching ratios of nonfragmented doubly charged clusters have been interpreted on the basis of calculated internal energies of C{sub n}{sup 2+} due to single ionization of C{sub n}{sup +} clusters using the IAE model. This allowed estimates of the minimum energies required to fragment these C{sub n}{sup 2+} species to be derived.« less
  • Decrease in the elastic scattering cross sections for atoms and ions in high-energy binary collisions is studied. (AIP)
  • The dissociation of fast ionic hydrogen clusters H[sub [ital n]][sup +] by collision with helium atoms has been studied for various incident cluster masses ([ital n]=5,7,...,31) at 60 keV/amu energy. Absolute dissociation cross sections have been measured. No shell effect is observed. As expected, the cluster dissociation cross section increases with [ital n] but exhibits a quasilinear dependence in contrast with the [ital n][sup 2/3] dependence previously observed [M. Chevallier [ital et] [ital al]., Z. Phys. D 2, 87 (1986)] with argon atoms in the same velocity range.
  • Neutral products from dissociative collisions of triatomic hydrogen like ions incident on He atoms were studied. Absolute differential and total cross sections are reported in the energy range of 1.25 and 5.00 keV for scattering angles between -5 deg. and 5 deg. The differential cross sections have a decreasing behavior with a slight structure around 2.0 deg. . The total cross sections show no dependence on the projectile mass at equal velocity. The cross sections are between 4x10{sup -17} cm{sup 2} and 2x10{sup -16} cm{sup 2}. A polynomial fit of fourth order was adjusted to the data indicating a maximummore » at 3.5 keV/amu, and showing an agreement with a previous work for H{sub 3}{sup +} at high energies.« less