SPIN-ORBIT-COUPLING IN VARIATIONAL QUANTUM MONTE-CARLO CALCULATIONS

We have studied the influence of valence electron correlation on the t otal angular-momentum eigenstates emerging from the 6s(2) 6p(2) valenc e configuration of Pb and isoelectronic ions Bi+ and Po2+ using a vari ational quantum Monte Carlo method and relativistic pseudopotentials. The wave functions consist of a Jastrow factor and an antisymmetric or bital-dependent part which describes the states of the atom in an inte rmediate coupling scheme. A correlated sampling method has been used t o reduce the statistical fluctuations; making it possible to obtain su fficiently precise energy differences, which are necessary for a discu ssion of differential correlation effects in the fine-structure splitt ings. It has been demonstrated that our ansatz reproduces well the res ults of relativistic pseudopotential and fully relativistic all-electr on configuration interaction calculations.