Relativistic Intermediate-coupling Calculations for Ions of the Beryllium Isoelectronic Sequence

Abstract

Relativistic intermediate-coupling wavefunctions are used to evaluate wavelengths and oscillator strengths for the resonance transition 2S2 'SO -+ 2s2p 'P~ and the intercombination transition 2S2 'SO -+ 2s2p 3p~ for iron, krypton, molybdenum and tungsten beryllium-like ions. The convergence of the results with respect to the basis set of orbitals is considered. It is shown that the same degree of accuracy can be achieved by using the three configuration basis composed of 2S2, 2s2p and 2p2. The question of at what stage the Breit interactions should be included in the Hamiltonian is discussed. We also compare our calculated 2S2 'SO -+ 2s2p 3p~ intercombination oscillator strengths with those deduced from beam-foil experiments for iron and krypton