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 using Davidson's iterative diagonalization scheme. The accuracy of the approach has been investigated by calculating low-lying transitions of Xe atom, HI molecule and spin forbidden 1S0 to 3P1 and spin allowed 1S0 to 1P1 transitions in a few closed shell cations. Additionally, applications aimed at evaluating the L-edge X-ray absorption spectrum (XAS) of Ar atom is studied. The calculated results show good agreement with the earlier theoretical studies and experimental values.