Exponential gap law for atom—diatom inelastic scattering

✍ Scribed by Donald F. Heller

• Publisher: Elsevier Science
• Year: 1977
• Tongue: English
• Weight: 677 KB
• Volume: 45
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(77)85210-x

✦ Synopsis

A very simple (semiclassical) treatment of nonreactive atom-diatom collisions permits the analytic approximation of inelastic state to state scattering cross sections. The derived energy dependence of these cross sections is found to be reasonably independent of the form of the effective (model) scattering potential indicating some generality of applicabtity.

These results provide a generalization of the famdiar (empliical) Iinear surprisal (exponential gap) reIationship encountered in vzbratronally or rotational& inelastic scattering. Explicit expressions are given for the surprisaf parameters of Levine and Bernstein et al. These are evaiuated for several rotationally inelastic processes. The theory is seen to predict correctly the observed surprisal slopes and their energy and mass dependence.

It also predicts deviations from the linear surprisal form when states having high internal energies are involved. For the more complex case of both vibrationally and rotationally inelastic scattering certain simple behavior of the surprisals (inelastic cross sections) is expected in limiting energy regions. We susest that linear surprisals wdl not be generai for systems which do not conform to the model assumptions. We conclude that linear surprisaIs are manifestations of scattering processes which are dom~ated by the translational dynamics. Tnc surprisal slope measures the range of the effective scattering potential. The details of the potential surface therefore are relatively unimportant. * See, for example, the surprisal plots of ref. (61 which are virtually identical up to scaling of the energy Mis.