Relativistic Calculation of Specific Mass Shifts for Ar+, Ni, Kr+, and Ce+ using a multi-configuration Dirac-Fock Approach

An extension of the multi-configuration Dirac-Fock (MCDF) program for calculation of the specific mass shift (SMS) is described. The SMS values obtained from this relativistic program are shown to exhibit a trend: the higher the Z-value of the atom, the better the agreement with experiment and the greater the discrepancy with the non-relativistic results. The various modes (average level, optimal level, etc.) for achieving an approximate wavefunction, and their impact on the relativistic SMS values, are explored. Comparisons are made with other theoretical SMS values as well as with experiment for Ar, Ni, Kr, and Ce with new results reported for each atom.