Study of the Fluorescence Polarization of the He‐β Characteristic Line Radiation

ABSTRACT This manuscript presents a theoretical evaluation of the structural properties, excitation cross sections, and fluorescence polarizations of the characteristic line radiation after electron impact of the plasma‐embedded atom. The analysis is performed using the distorted wave method within the framework of relativistic theory, addressing the Dirac equation with an adapted analytical potential that captures the shielded interactions of the hot dense plasma. Such an analytical potential is obtained by solving the Poisson equation and employs self‐consistent field ion‐sphere simulations to elucidate the interactions between charged particles. The structural parameters, including energy levels and spectral line shifts, are determined by applying the effective Hamiltonian. The collision parameters, such as the total and magnetic sublevel angle‐integrated cross sections, are calculated using the fully relativistic distorted wave approach, where in both Dirac‐Coulomb Hamiltonian and scattering matrix element, the traditional Coulomb interaction is purposefully replaced by a shielded analytical potential. These cross sections are the essential parameters for determining the polarization of the characteristic fluorescence radiation and the angular distribution of the polarization. Relativistic effects, including the Breit interaction and the Quantum electrodynamics corrections, are incorporated to enhance the accuracy of the methodology. As an example, detailed calculations for the 1s excitation of the He atom embedded in a plasma by electron impact are performed. The effects of the hot dense plasma on the atomic structure, scattering process, and the fluorescence polarization of the characteristic line radiation are investigated. Numerical results illustrate that the energy levels move closer to the continuum threshold as the confinement becomes more pronounced. The cross sections show a consistent decrease with increasing confinement, while the polarizations of the fluorescence emission show only small changes. Our results, when compared with the existing experimental and theoretical data for the plasma‐free case, show a high degree of congruence. The present study not only provides a valuable method for the analysis of plasma effects, but also has significant relevance for applications in various fields such as the study of stellar atmospheres and the field of fusion research.