Hartree-Fock calculations for the 4d⁹5s²5p⁶4f configuration in La IV

Recently discrete resonances in the photoabsorption spectrum of La near the 4d electron threshold have been identified as combinations between the ground-state of La IV, 4d 10 5s 2 5p 6 1 S 0 , and the J=1 levels of the 4d 9 5s 2 5p 6 4f configuration, the strongest combination being with 4d 9 4f 1 P 1 . The agreement was satisfactory between energies from observations and from ab initio calculations except for 1 P 1 , for which the energy predicted by using wavefunctions determined for the mean energy of the whole configuration is about 14 cV too high. The present Hartree-Fock calculation for the 1 P term removes half of this discrepancy. Part of the remaining discrepancy may be caused by solid state effects. The relevance of this result for calculations of photoionization in Ar I and Xe I is pointed out.