Electron Capture Processes in Slow Collisions of Plasma Impurity Ions with H, H2, and He

Abstract

Electron capture in collisions between plasma edge impurity ions and atoms is the most important heavy-particle collision process in the plasma edge region. While excitation and ionization of the main plasma edge neutrals, H, H2, and He, by slow plasma impurity ions are subject to adiabatic evolution constraints, electron capture can proceed via localized nonadiabatic couplings. For ions in higher charge states, the number of nonadiabatic couplings may become very large, and the electron capture process assumes a quasi-resonant character with large (10-15 – 10-14 cm2) cross section.