Eden, S.; Tabet, J.; Samraoui, K.; Louc, S.; Farizon, B.; Farizon, M.; Ouaskit, S. and Märk, T. D.
Absolute cross sections for the dissociation of hydrogen cluster ions in high-energy collisions with helium atoms.
Physical Review A, 73(2)
Absolute dissociation cross sections are reported for Hn+ 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 Hn+ dissociation cross sections upon n is developed with reference to expected series of geometrical shells of H2 molecules surrounding a H3+ core. Recent calculations identify n=9 as corresponding to the first closed H2 shell [e.g., tich 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.
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