Electron translation factors in orienting charge transfer collisions

The role of the electron translational factors (etf) in the semiclassical theory of charge transfer is addressed with respect to orientation effects and possible propensityrules in s-p and p-p capture processes. It is shown that orientation effects can be understoodin the light of the intuitive classical ‘rolling ball’ and ‘velocity matching' arguments andanalysed using the Larsen-Taulbjerg first-order approximation to the etf. Emphasis isplaced on investigating resonant p-p transfer which is a crucial test case for the effects ofetf on orientation dependences. The predictions are exemplified by four-state closecoupling calculations for Na(3p¹_m)) + Na⁺→ Na⁺ + Na(3p¹_m) resonant transfer taking fullaccount of etf. Some problems involved in comparing experimental data at small scatteringangles with theoretical predictions are discussed.