Configuration Interaction and the hfs of theslConfiguration

Abstract

Accurate hfs measurements in both the singlet and the triplet states of the first excited configuration of the group II elements have recently been obtained. These results have shown that the hfs of the singlet state cannot be reliably predicted from a knowledge of the hfs of the triplet states. A modification of the Breit-Wills theory for the hfs of the $\mathrm{sl}$ configuration is developed which takes into account the fact that the $l$ electron has a different radial wave function in the singlet and the triplet state. The theory introduces a new parameter $\lambda$ (the ratio of the off-diagonal to the diagonal matrix element of the spin-orbit operator) which can be estimated from the fine structure. This modified Breit-Wills theory is compared to recent experimental data for first excited $\mathrm{sp}$ configuration of Cd, Ba, and Hg. For Hg and Ba excellent agreement between all the hfs of the $\mathrm{sp}$ configuration is obtained. For Cd a significant improvement is obtained but a discrepancy still remains which, however, can be explained.