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Scattering of high-incident-energy Kr and Xe from ice: Evidence that a major channel involves penetration into the bulk
K.D. Gibson, D.R. Killelea, H. Yuan, J.S. Becker, S. Pratihar, , S.C. Kohale, W.L. Hase, S.J. Sibener
Published in
Volume: 116
Issue: 27
Pages: 14264 - 14273
The scattering of high kinetic energy (1-6.5 eV) xenon and krypton atoms from ice was experimentally measured and theoretically modeled. The ice efficiently accommodates translational energy, but the extent to which the energy is quenched suggests the mechanism for the highest energies and near-normal incidence angles involves more than interaction with just the molecules at the ice surface. Simulations show that for these conditions the xenon penetrates into the selvedge. This penetration into the solid manifests experimentally in that the postcollision translational energy is essentially independent of the incident translational energy. This observation is in stark contrast with what is usually the situation for scattering from a surface. Finally, postexposure desorption measurements showed that some of the incident gas atoms were trapped in the bulk of the ice at temperatures well above where the absorption is thermodynamically stable. The above evidence leads to the conclusion that under conditions of near-normal angles of incidence and high collision energy, much, if not most, of the rare gas penetrates below the ice surface and into the selvedge. A fraction is stably embedded in the near surface region of the ice, whereas the remaining rare gas escapes with two distinct velocity distributions; the first is a result of a thermal process and the second, faster distribution, is the result of ejection from the solid. © 2012 American Chemical Society.
About the journal
JournalJournal of Physical Chemistry C