Role of the Anisotropy of the Potential in Quenching of Glory Extrema in Atom–Diatomic Molecule Scattering

Abstract

Damping of the glory undulations in the velocity dependence of the total cross sections for atom–molecule scattering was first observed by Gislason and Kwei and (correctly) explained by them qualitatively in terms of inelastic and reactive processes concurrent with anisotropic elastic scattering. Subsequent experiments by Helbing and Rothe confirmed the quenching phenomenon and extended the range of systems exhibiting such behavior. The present theory deals mainly with nonreactive atom–diatomic collisions, considering the coupled equations in the total angular-momentum representation and taking full cognizance of the anisotropic distortion of the potential. The resulting equations yield a lower bound on the degree of quenching, but should be fairly generally applicable except for extremely reactive systems of the “stripping” type. The extent of the damping and its velocity dependence is expected to be increased for systems of larger reduced mass with deeper van der Waals potential wells (ε), larger-size parameters (rm), and greater short-range anisotropy coefficients. The equations suggest a simple method to retrieve the short-range anisotropy coefficient of the potential from quenching data.