Relativistic SCF calculations of transitions in the principal and intercombination series of mercury

Abstract

Relativistic self-consistent-field (SCF) calculations of oscillator strengths, excitation energies and singlet-triplet splittings are reported for the 6 s 2 1 S 0-6 snp 3 P 1, 1 P 1 transitions in mercury with 6 ⩽ n ⩽20. Intermediate coupling is assumed for excited 3 P 1, 1 P 1 states, and for the ground 6 1 S 0 state additional 6 p 2 1 2 , 6 p 2 3 2 configurations are admixed to account for much of the ground-state intravalence correlation. The core-valence correlation is included within the core-polarization approximation. We show that theoretical explanations of the intensity anomaly at high n, which are based on intermediate coupling, require that calculations performed in the optimized level (OL) scheme include effects which affect the 3 P 1 and 1 P 1 states separately. These calculations cannot explain the anomaly because of extremely strong cancellation in the radial integrals for the 6 1 S 0- n 3 P 1 transitions. The calculations suggest that intermediate coupling is not the only factor responsible for the observed intensity anomaly, and we expect other correlation effects (represented by the mixing of different non-relativistic configurations) to play an even more important role. In the frozen-core approximation used in our SCF calculations, fairly reliable excitation energies and singlet-triplet splittings are obtained simultaneously with the oscillator strengths, provided the Hg +-like frozen core is used rather than the core frozen in the 6 1 S 0 ground state.