The polarized frozen-core approximation

Abstract

We have calculated orbital wave-functions and ionization energies for a large number of singlet and triplet s-, p- and d-states of Be(I), all of which are members of series which converge to the Be(II)2S limit. The simple frozen-core Hartree-Fock model yields energy levels which agree with observations to within 5% for most excited states, but there are substantial discrepancies for the low-lying excited states and especially the 2s- and 2p-states. By including an l-dependent core-polarization potential with an adjustable cut-off parameter, we are able to reproduce the observed ionization energy of the lowest member of each series (except the 2snd 1D series) and obtain improved agreement for the higher members. Both the unpolarized and the polarized frozen-core energies and orbitals have been employed to calculate electric dipole oscillator strengths. Comparisons with results of refined superposition of configuration calculations for a number of 1P0-1S transitions suggest that the introduction of a polarization potential yields substantial improvement in the derived oscillator strengths. Show more