Δ<i>M</i> <i>j</i> transitions in homonuclear molecule scattering off corrugated surfaces. Square and rectangular lattice symmetry and purely repulsive interaction

Abstract

In this paper, we present the first formal and computational studies of Δmj transitions occurring in homonuclear molecule-corrugated surface collisions. The model potential is a pairwise additive one which correctly incorporates the fact that Δmj transitions occur only for corrugated surfaces (provided the quantization axis is chosen to be the average surface normal). The principal results are: (a) Δmj transitions are extremely sensitive to lattice symmetry; (b) strong selection rules obtain for specular scattering; (c) the magnitude of Δmj -transition probabilities are strongly sensitive to surface corrugation; (d) the Δmj transitions depend strongly on diffraction peak; (e) the ratio of molecular length to lattice dimension (r/a) has a strong influence on the magnitude of Δmj -transition probabilities [with the probabilities increasing as (r/a) increases]; (f) Δmj rainbows are predicted to occur as a function of the (r/a) ratio increases; (g) Δmj transitions and the Δmj rainbow are expected to accompany Δj-rotational rainbows; (h) such magnetic transition rainbows accompanying Δj rainbows are suggested as an explanation of recent experimental observations of quenching of NO polarization for larger Δj transitions in NO/Ag(111) scattering.