Collinear fast-beam laser spectroscopy has been used to measure the hyperfine splittings and the isotope shifts in the 4${\mathit{p}}^4$4d ${}_{}{}^4{}_{}{}^{}$${\mathit{D}}_{7/2}$–4${\mathit{p}}^4$5p ${}_{}{}^4{}_{}{}^{}$P${\mathrm{°}}_{5/2}$ (λ=729 nm) transition of singly ionized Kr. The measured isotope shifts are very large due to a large specific-mass effect that is caused by the strong momentum correlations of the 4d electron with the core electrons. Hartree-Fock and multiconfiguration Hartree-Fock (MCHF) calculations of the specific-mass shift were carried out and are compared to the measurements. The MCHF calculation yields excellent agreement with the experimental results.

• Received 5 December 1991

DOI:https://doi.org/10.1103/PhysRevA.45.6459