Quantum Scattering Theory of the Complex Level Shift of Spectral Lines in Plasmas

Abstract

Both the electron impact broadening and shift of spectral lines in plasmas are consistently recognized as the complex level shift by quantum scattering theory based on the impact approximation. As a realization of the theory, the transition matrix is evaluated by the R-matrix method for the relevant states connected by a allowed transition. It is proved that the center of a typical Lyman-α line of ionized helium gives a small red shift in contradiction to the current phenomenological prediction in the effective charge approximation. It is also shown that the main contribution to the shift comes from close collisions with perturbers having low angular momenta, while the width is composed of a considerable number of partial waves.