Influence of hot and dense plasmas on photoionization dynamic of hydrogen-like ions

Abstract

In hot and dense plasma of solar and stellar interiors, Coulomb potentials between the nucleus and electrons are screened due to the complicated many-body interactions, resulting in significant alterations in atomic structures and dynamic properties of the embedded ions as well as the macroscopic transport properties, such as opacities. Here, the photoionization dynamics of the n ≤ 2 states of hydrogen-like ions (He⁺, B⁴⁺, Ne⁹⁺, P¹⁴⁺, Ca¹⁹⁺, Fe²⁵⁺) are investigated employing the atomic-state-dependent (ASD) screening model based on the multiconfiguration Dirac-Hartree-Fock method. It is found that the photoionization cross sections are significantly increased by the plasma screening effects, especially for the denser plasmas. For example, the photoionization cross section of 2p_3/2→εd_3/2 for Ne⁹⁺ increases nearly 10 times at a condition of T_e =150 eV and n_e=1.0 × 10²⁵ cm^-3. The present results from the ASD model show reasonable agreement with the classical Debye Hückel (DH) model in low-density plasmas, however, the DH model overestimates the densities of plasma electrons in dense plasmas due to neglecting the electron degeneracy effects. The influence of plasma screening on cross section decreases with increasing atomic number and is more significant for the excited states than the ground state. The photoionization cross sections of the ground state approximately follow the scaling law as atomic number varies, but this law can not be applied to excited states because plasma electron distribution in the ASD model depends on specific bound states. The present investigation can be applied to study the opacity under solar and stellar interior conditions.