6S AND 4F IONIZED STATES OF THE LANTHANIDES CALCULATED BY NUMERICAL AND ANALYTICAL HARTREE-FOCK METHODS

The ground states, as well as the 6[ital s] and 4[ital f] ionized states of Ba, Cs, and lanthanide atoms from La to Lu, are calculated with the nonrelativistic numerical Hartree-Fock (HF) method and an analytical HF method with Gaussian-type functions (GTF's). It is shown that the nonrelativistic HF calculations well reproduce the experimental trends on the 6[ital s] and 4[ital f] electron ionizations, although the calculated 6[ital s] ionization potentials (IP's) are smaller and the calculated 4[ital f] IP's are larger than those given by experiment. The relativistic HF calculations with GTF's are also performed on some selected atoms. The 6[ital s] IP's given by the relativistic HF method are closer to experiment than those given by the nonrelativistic HF methods. The relativistic corrections make 4[ital f] IP's smaller than those of experiment. Since the correlation effects increase the IP's obtained by the HF calculations, the inclusion of the relativistic effects is indispensable in discussing IP's quantitatively.