Classical Heavy-Particle Trajectories for Electron Capture inH+-He Collisions and for Other Asymmetric Collisions

Abstract

The method of perturbed stationary states, in a two-state approximation, is used to obtain semiclassical differential cross sections for electron capture or excitation in asymmetric ion-atom collisions at energies of the order of 1 keV. Two cases are discussed. In case A it is assumed that transitions between the two states occur only near a fixed internuclear separation; in case B it is assumed that they occur only near the distance of closest approach. Case B is studied in the limit of weak coupling; case A is studied both with and without this assumption. It is found that in each case the differential cross sections can be interpreted in terms of classical trajectories calculated from the potentials for the initial and final molecular states of the ion-atom system. It is also found that the impact-parameter calculation of the differential cross section may be considerably in error except at small impact parameters. The results for case A are shown to apply at least approximately to ${\mathrm{H}}^{+}$-He collisions and are compared with the experimental data of Helbig and Everhart.