Field shift crossed second-order effects in dNsp configurations

In configurations containing open s subshells, far-configuration mixing ('crossed second-order effects') leads to different electron change densities at the nucleus for the various Russell-Saunders terms and thus to different field isotope shifts. For nd N (n+1)s (n+1)p configurations (n=3, 4, 5; N=1-10) the electron charge densities D of pairs of terms belonging to parents with the same multiplicity calculated using the Hartree-Fock computer code of Froese Fischer (1978). Usually, the term with the higher multiplicity has the larger density. The density difference Delta D increases linearly with the number of d electrons up to the half-filled shell and then decreases. The terms belonging to the parent with the higher multiplicity show larger values of Delta D than those belonging to the parent with the lower multiplicity. The effect increases with the principal quantum number n; it depends on the spins of the parent and grandparent terms but not on their angular momenta. The Hartree-Fock results of Delta D were used to calculate field shift differences between the corresponding terms. The comparisons of calculated and experimental field shift differences shows that the non-relativistic Hartree-Fock method correctly predicts their sign and order of magnitude.