SPIN-ORBIT CI STUDY ON MULTIPLET TERMS OF TRIVALENT LANTHANIDE CATIONS

In this paper we calculate the low energy spin-orbit multiple; terms o f trivalent lanthanide cations Ce3+ to Yb3+, except for Gd3+, with thr ee different RECPs, including the spin-orbit effect explicitly, to ass ess their reliability. Although there is fairly good agreement with ex periment for the ground LS multiplet splittings, implying the accuracy of the spin-orbit Hamiltonian, the agreement is less for the higher L S terms. The source of the error was found to be the significant semi- core correlations in the 4d, 5s, and 5p shells, which have very strong effects on the spin-free excitation energies, The degree of the inter mediate coupling is also studied and related to the deviation from the Lande interval rule. The differences between the intermediate couplin g method and the fully variational spin-orbit CI method are numericall y analyzed. (C) 1998 Elsevier Science B.V. All rights reserved.