Parameters of Isotope Shifts for 2s2p 3,1P1 → 2s2 1S0 Transitions in Heavy Be-Like Ions**Supported by the National Natural Science Foundation of China under Grant Nos 11874090, 11604385, 91536106 and 11204374, and the Research Project of National University of Defense Technology under Grant No ZK17-03-11.

Abstract

The field shift and mass shift parameters of the 2s2p 3,1P1 → 2s2 1S0 transitions in Be-like ions (70 ≤ Z ≤ 92) are calculated using the multi-configuration Dirac–Hartree–Fock and the relativistic configuration interaction methods with the inclusion of the Breit interaction and the leading QED corrections. We find that the mass shift parameters of these two transitions do not change monotonously along the isoelectronic sequence in the high-Z range due to the relativistic nuclear recoil effects. A minimum value exists for the specific mass shift parameters around Z = 80, especially for the 2s2p 3P1 → 2s2 1S0 transition. In addition, the field shifts and mass shifts of these two transitions are estimated using an empirical formula, and their contributions are compared along the isoelectronic sequence.