Hyperfine structures in 167Er II: Measurements of high 4f125d levels and ab initio multiconfiguration Dirac-Fock calculations.

Abstract

Hyperfine-structure measurements in high 4${f}^{12}$5d metastable levels of $^{167}\phantom{\rule{0ex}{0ex}}\mathrm{i}\mathrm{i}$ have been carried out to supplement earlier data on the low 4${f}^{12}$6s levels. Ab initio multiconfiguration Dirac-Fock (MCDF) calculations have been performed, and the effects of core excitations and configuration interaction have been investigated. While good agreement between experiment and calculation was found for the low 6s levels, a less clear interpretation emerges from the higher 6d levels. This points directly to the problems in the MCDF scheme in understanding the effects of core excitation and configuration interaction.