Relativistic effects in the variable-screening model

The variable-screening model devised for a quantitative treatment of screening effects in slow (quasimolecular) ion-atom collisions is extended to include relativistic effects. Relativistic correction terms corresponding to a relative energy correction of second order in the electron velocity are incorporated into the effective molecular single-electron Hamiltonian. The model is applied to the calculation of relativistic molecular-orbital correlation diagrams for the quasimolecular systems Br+Br, Xe+Xe, and I+Au. A detailed comparison of our results with the results of relativistic calculations for (unscreened) one-electron systems and calculations based on self-consistent field methods is performed. The agreement with Dirac-Fock-Slater results is fairly good, and could be improved further by read-justing the values of the parameters in the atomic potentials used to construct the effective molecular potential.