Quadrupole Antishielding Factors for Rare-Earth and Some Other Heavy Ions

Sternheimer quadrupole antishielding factors (γ_∞) are reported for several rare-earth ions and for several ions isoelectronic with I^- and Br^-. Radial excitations were obtained using the self-consistent-field unrestricted Hartree-Fock method ("orbitally polarized" H-F method) described previously. Comparisons with perturbation-theory estimates of Sternheimer are presented. It is concluded that a roughly constant value of γ_∞≈-80 is appropriate for the trivalent rare-earth ions. The relation to experiment of theoretical estimates of γ_∞ for positive and negative ions is discussed.