Energy differences between 4f(n+1)5d(0)6s(2) and 4f(n)5d(1)6s(2) electron configurations for the lanthanide atoms - art. no. 012503

We study the energy difference DeltaE(n) between the 4f(n+1)5d(0)6s(2) and 4f(n)5d(1)6s(2) configurations of the entire neutral lanthanide series, whe re it runs from 0 (La) through 13 (Yb). The DeltaE(n) values obtained by nu merical multiconfigurational Dirac-Fock (MC-DF) calculations are lower than experiment, while those given by nonrelativistic self-consistent-field (NR -SCF) calculations are larger than experiment. The difference between the M C-DF and NR-SCF DeltaE(lt) values is about 3-5 eV. If we add the correlatio n energy corrections obtained by nonrelativistic second-order perturbation calculations to DeltaE(n) given by MC-DF calculations, the resulting values of DeltaE(n) for the neutral lanthanides agree with experiment to within 1 .0 eV, except for La and Yb.