Behaviors of Electron Capture Cross Sections in the Intermediate Velocity Regime on Ion-Atom Collisions

Abstract

The behavior of electron capture cross sections in the intermediate velocity regime are classified into two types: one showing moderate monotonic change against collision velocity and the other showing noticeable change with a clear maximum in the intermediate velocity regime. In order to reproduce the two types of velocity dependencies for the collision system of low-ionization-stage ions and light atoms, we proposed a velocity matching model for an electron capture process in the intermediate velocity regime, taking the characteristics of the intermediate velocity collisions into consideration; i) collisions with a small impact parameter are effective. ii) Finite relaxation time necessary for electron capture reduces the cross section proportionally to 1/V, as collision velocity V increases. The limitations of the application of this model are also discussed.