Theoretical evaluation of excitation cross section and fluorescence polarization of a solid-density Si plasma

Abstract

In this article, a fully relativistic approach is proposed to precisely predict the electronic structures, spectral properties, cross sections, and degrees of linear polarization of light emitted after excitation of plasma-embedded ions by electron impact, taking into account the plasma shielding effects on the atomic structures and collision dynamics, in addition to the contributions of Breit interaction and quantum electrodynamics effects. The scheme employs the effective shielding potential deduced from a solution of Poisson equation, based on the self-consistent field ion-sphere simulations to explain the interactions among the charged particles, where the perturbation correlation Dirac–Coulomb Hamiltonian is constructed. The simple and understandable form makes it a good substitute for complex self-consistent field calculation. As an illustrative example, a comparative investigation regarding the influences of different plasma temperature and density parameters on the level energies, transition rates, integrated total/magnetic sublevel cross sections, and linear polarizations of the radiation following electron-impact excitation of Si XIII (a solid-density Si plasma) is carried out. Numerical results show that the plasma density effect can significantly affect the atomic structures and collision cross sections, yet has limited influence on the polarization characteristics. A comparison of our calculations with other results, when available, is made. The advanced approach presented here not only opens a novel window for exploring the atomic dynamics processes in hot and/or dense plasmas, but also provides important information about polarization of the line emission. This study is beneficial for the high energy density physics, laser-produced plasmas, and astrophysical applications.