Calculation of Stark-induced absorption on the $6s6p{{}^{3}P}_1–6s^2{{}^{1}S}_0$ transition in Hg

We carry out relativistic many-body calculations of the Stark-induced absorption coefficient on the 254-nm $6s6p{{}^{3}P}_1\left(F=1/2\right)–6s^2{{}^{1}S}_0$ line of ${}^{199}\text{H}\text{g}$ atom, the effect considered before by and Lamoreaux and Fortson [Phys. Rev. A 46, 7053 (1992)] using a simple central field estimate. The Stark-induced admixing of states of opposite parity opens additional $M1$ and $E2$ transition channels. We find that the resulting $M1\text{−}E1$ absorption dominates over $E2\text{−}E1$ absorption. The value of the $E2\text{−}E1$ absorption coefficient depends strongly on the details of treatment of the correlation problem. As a result, our numerical values differ substantially from those of the earlier central field calculation. Reliable calculation of this effect can enable a useful experimental check on the optical technique being used to search for a permanent electric-dipole moment of the ${}^{199}\text{H}\text{g}$ atom.