Ionic excitation in dense, two-component plasmas: Effect of energy level shifts

Abstract

Collisional excitation rates for an ion immersed in dense electron–ion two-component plasmas are formulated by taking into account shifts of ionic energy levels due to static and dynamic plasma perturbations. The theory is based on the equations of motion for density matrices combined with the statistical theory of plasma density fluctuations. Through separation of the time scales associated with electron- and ion-density fluctuations, the electron-induced excitation rates are derived, where energy level shifts arising from quasistatic electric microfields by screened plasma ions as well as those arising from time-averaged spherical plasma polarization are considered. As a numerical example, the transition rates among the 2s and 2p fine-structure levels of a Ne9+ ion in dense hydrogen plasmas are calculated. It is demonstrated that, at sufficiently high plasma densities, the ion microfields cause Stark splittings and affect the excitation rates significantly through modifications of the generalized oscillator strengths.