Multiconfiguration Dirac-Hartree-Fock calculations for Hg and Cd with estimates for unknown clock-transition frequencies

By use of the grasp2018 package we perform multiconfiguration Dirac-Hartree-Fock (MCDHF) calculations with configuration interaction (CI) for the S01 and P0,1o3 levels in neutral cadmium and mercury. By supplying the resultant atomic state functions to the ris4 program, we evaluate the mass- and field-shift parameters for the S01-P0o3 (clock) and S01-3P1o (intercombination) lines. We make revised estimates of the nuclear charge parameters λA,A′ and differences in mean-square charge radii δ(r2)A,A′ for both elements and point out a discrepancy with tabulated data for Cd. In constructing a King plot with the Hg lines we examine the second-order hyperfine interaction for the P0,1o3 levels. Isotope shifts for the clock transition have been estimated, from which we predict the unknown clock line frequencies in the bosonic Hg isotopes and all the naturally occurring isotopes of Cd.