Impulse Formalism for Atom-diatom Collisions
AIR FORCE GEOPHYSICS LAB HANSCOM AFB MA
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An exact formulation of the impulse approach IA, or quantum- mechanical spectator model, is applied to atom-diatom collisions. Results are compared with previous work on the IA, which has always involved the peaking approximation PA. The PA is seen to overestimate underestimate differential cross sections for processes involving projectile atom energy loss gain. The internal consistency of the IA is explored by subjecting it to semidetailed balancing. For small scattering angles the IA is seen to be an inadequate theory, probably due to the neglect of double-and higher collision terms in the multiple-collision expansion of the three-body T matrix. For large scattering angles, where the IA does appear to describe the scattering process accurately, the exact calculation is shown to give the same results as when only the energy- conserving on-the-energy-shell two-body processes are considered. An accurate approximation method is also developed for rapid computation of inelastic differential cross sections.
- Atomic and Molecular Physics and Spectroscopy