"A Classical Ensemble Model of Three-Body Collisions in the Point Contact Approximation and Application to Alignment Effects in Near-Resonant Energy Transfer Collisions of He Atoms with Rydberg Ca Atoms.''

N. Shafer-Ray, G. A. Parker and M.A. Morrison,

J. Chem. Phys. 113, 4274-4289 (2000).

065 ClassicalEnsemble.pdf

Abstract:  A classical ensemble model of three-body energy transfer in the point contact approximation is presented. This model yields cross sections for transitions between initial and final states defined by energy, magnitude of angular momentum, and projection of angular momentum along an axis of spatial quantization corresponding to the quantum numbers of the initial and final stationary states, n, l , m and n8, l 8, m8. Using a cross section that is differential in the final-state quantum numbers, the spatial constraints imposed by conservation of energy and angular momentum can be investigated even for comparatively small quantum numbers. When applied to the Ca(17d)1He ! Ca(18p) 1He energy transfer processes, the model sheds light on recently discovered alignment phenomena in collisions of rare-gas atoms with initially aligned Rydberg atoms. Materials for the implementation of this model are available from the authors via the Internet.

"Rydberg Electron Interferometry''

M. A. Morrison, E. G. Layton, and G. A. Parker, 

Phys. Rev. Lett. 84, 1415-1418 (2000).

061 RydbergElectron.pdf

Abstract:  A recent quantum mechanical study [W. Isaacs and M. A. Morrison, Phys. Rev. A 57, R9 (1998)] dis-covered pronounced oscillations in cross sections for near-resonant energy transfer collisions of rare-gas atoms with initially aligned Rydberg atoms. We analyze such collisions for 17 dm !18 pm 0 transitions in the Ca-He system semiclassically and show that the oscillations arise from a phase interference process unique to Rydberg target states. In addition to explaining the origin of these structures, this analysis explains their disappearance when the relative Ca-He velocity goes to infinity and/or the energy defect vanishes and their dependence on the initial and final magnetic quantum numbers of the transition.