Semiclassical calculations of cross sections for fine-structure transitions in Rb (62P) and Cs (82P) colliding with rare gas atoms

Abstract

Calculations of cross sections for fine-structure transitions in the second and third excited 2P state of rubidium and cesium, respectively, have been carried out using a semiclassical theory for collisions with ground state He, Ar, and Xe atoms. The primary difference from previous theories for the first 2P state of an alkali is the full formulation of the semiclassical theory in terms of molecular states of the alkali–rare gas atom complex. The molecular states are consistent with the interaction potential and both radial and rotational coupling are explicitly included in the calculations. In the collision energy range investigated (from threshold to 0.3 eV) the cross sections are found to have an undulatory structure, especially prominent for the Rb–Ar system. Except for the Cs–He system, the thermally averaged cross sections agree with experiment within a factor of 1.4–2.8. For cesium, these results reduce considerably the large discrepancy between previous calculations of Nikitin and Reznikov (1971) and experiment.