Study of energies and radiative properties of He-like ions within a dense plasma

Abstract

On the basis of the tensor expression for the Breit-Pauli Hamiltonian and the irreducible tensor theory for many-electron atoms, we have proposed a general analytical method for calculating atomic structures of highly charged ions under a dense plasma environment. In this method, the standard ion-sphere (IS) potential is used to represent the interaction between the charge particles. The Racah wave functions are obtained as the linear combinations of the multi-Slater wave functions. The angular interactions and spin sums are worked out using an irreducible theory of complex systems. Analytical formulas for the calculation of relativistic corrections, such as the mass correction, the one-body Darwin correction, the two-body Darwin correction, and the spin-spin contact interaction, are derived. Energy levels and radiative properties of He-like Al11+ and Ni26+ ions are considered for illustrative purposes. Systematic trends with respect to both the nuclear charge Z and the electron density Ne are observed for all calculated quantities. Self-consistent calculations of dense plasma effects on the atomic structure, based on the same IS potential, are also presented using fully relativistic multiconfiguration Dirac-Fock (MCDF) wave functions in the active space approximation with the inclusion of a finite nuclear size, the Breit interaction, self-energy, and vacuum polarization for comparison purposes. Comparison and analysis are made between our two sets of results and the available results in the literature. The effects of relativistic correlations are investigated in detail for the first time and are found to play an important role in the stability of these systems. The results of this study should be of great help in the modeling and diagnostics of astrophysical and laboratory plasmas.