Multiconfiguration Hartree-Fock study of the interaction between sp^6 and s^2p^4d in the CI i, Br i, and I i isoelectronic sequences with particular emphasis on the neutral halogens

Abstract

Multiconfiguration Hartree-Fock calculations for the lowest 2S term belonging to the sp62S + s2p4d configurations are presented for the first members of the Cl i, Br i, and I i isoelectronic sequences. The wave functions are used to calculate gf values for the transitions to the ground term and to calculate the hyperfine structure of the 2S terms. For the halogens the 2S term is found to be a nearly 50% mixture of sp6 and s2p4d which agrees qualitatively with results obtained by Cowan, Radziemski, and Kaufman by a series perturbation calculation. It is argued that for the purpose of isoelectronic comparison it is valid to consider the lowest 2S terms as belonging to the same isoelectronic series even though the dominant eigenvector component in one sequence (Br i) changes along the series in the MCHF approximation.