New screening coefficients for the hydrogenic ion model including l-splitting for fast calculations of atomic structure in plasmas

Abstract

New screening coefficients are given for calculating the energy levels of many-electron atoms in the hydrogenic ion approximation including l-splitting. This model allows fast computation of various atomic parameters (one-electron energies, ionization potentials, etc.) for all ionization stages of any element with no restriction concerning the maximum nl subshell. Part of the screening coefficients have been obtained from numerical fits over a large data base containing ionization potentials and excitation energies of ions. The others have been extrapolated by means of regularities deduced from the adjustment procedure. The mean and root mean square errors are better than 5% and 16.2%, respectively, for the 15 636 data considered. Some properties of the new screened hydrogenic model are studied, such as the filling competitions between several subshells of the lanthanides. The meaning of one-electron energies available from the total ion energy is discussed and the status of the self-screening term in plasmas in local thermodynamic equilibrium is briefly addressed. These notions are of great importance for coherence between the statistical treatment of such media and the calculation of their spectral properties.