Analysis of atomic electric dipole moment in thallium by all-order calculations in many-body perturbation theory

A procedure is presented for calculations of double-perturbation problems in the coupled-cluster formalism. With use of this method to include to all orders the correlation effects of single and pair excitations, the enhancement factor R=-585 is obtained for the electric dipole moment (EDM) in atomic thallium. Equations for EDM perturbed single-excitation amplitudes are solved by diagonalization to take into account mixing between excited core states, and perturbed pair functions are introduced to incorporate correlation effects. Considering contributions from higher-order perturbation terms, we estimate the accuracy of the obtained enhancement factor is approximately at the 5–10 % level.