Relativistic corrections to atomic energy levels

Abstract

The relativistic effects on bound levels of atomic systems with particular application to systems of astrophysical importance are investigated by including the most important contributions to the low Z Pauli approximation for the Hamiltonian. This work represents an extension of a general purpose computer program for calculating non-relativistic energy levels of complex atoms, described by Eissner and Nussbaumer (abstr. A10729 of 1970). Their algebraic approach has been adapted to the problems of evaluating matrix elements of the relativistic operators. In particular the program should give fairly good intermediate coupling wave functions. Thus it may be used as a basis for the calculation of intermediate coupling collision strengths and oscillator strengths. Numerical results are given for the magnesium I, sodium I and fluorine I isoelectronic sequences. In each case the calculations reproduce the observed Z dependence of the term differences in a much more satisfactory way than the non-relativistic calculations. Also calculations of spin-orbit parameters are found to compare well both with observed and the calculated parameters of other workers.