Spectral Line Shifts Produced by Electron Collisions in HeII Plasma

Abstract

Spectral line shifts for a few low-lying allowed transitions of ionized helium in the thermal plasma are investigated from a view-point of the quantum scattering approach based on the impact approximation with the aid of the R -matrix method.The short-time fluctuations of a field due to e]ectrons close to the radiating ion are fully taken into account and are expressed in terms of transition matrices for the lowest six states of the radiator. It turns out that the line center of Lyman-β undergoes only a small red shift whereas those of each component of Balmer-α undergo remarkable red shifts. All the level shifts are derived from close collisions with the perturbers incident upon the internal region of the configuration space describing the scattered electron and the target. The results are discussed and compared with experimental shifts as well as with existing theoretical results for the line shift.