Analytic calculation of transition dipole moment using four-component relativistic equation-of-motion coupled-cluster expectation value approach

We have developed an efficient scheme for the calculation of transition properties within the four-component relativistic equation-of-motion coupled cluster (EOM-CC) method using the expectation value approach. The calculation of transition properties within the relativistic EOM-CC framework requires the solution of both right and left eigenvectors. The accuracy of the approach has been investigated by calculating low-lying transitions of a Xe atom, a HI molecule, and spin forbidden 1S0 → 3P1 and spin allowed 1S0 → 1P1 transitions in a few closed shell cations. In addition to the valence spectra, the relativistic EOM-CCSD expectation value approach is particularly suitable for simulating the L-edge x-ray absorption spectrum (XAS). The calculated results show good agreement with the earlier reported theoretical studies and experimental values.