The spin-allowed and spin-forbidden 5s 2 1 S 0-5s5p 1 P 1,3 P 1 transitions in strontium isoelectronic sequence

Abstract

Relativistic multiconfiguration Dirac-Fock (MCDF) transition energies and oscillator strengths are determined for both the spin-allowed 5s21S0-5s5p1P1 and the spin-forbidden 5s21S0-5s5p3P1 transitions in the strontium isoelectronic sequence. The modest relativistic configuration mixing to represent intravalence correlation is combined with a polarization model to account for valence-core electron correlations. The multiconfiguration Dirac-Fock calculations are performed in an ‘average level’ scheme; however for neutral strontium and singly ionized yttrium a thorough comparison of the ‘average’ and the ‘optimal level’ schemes is presented. The average level scheme, though less accurate for the neutral end of the sequence, avoids the convergence problems encountered for highly ionized systems, where the 5s 5p3P1,1P1 states are raised owing to the collapse of the 4d3/2, 5/2 spin-orbitals in the isoelectronic sequence and, thus, allows us to extend our study to multiple charged ions (throughW36+). Since for such systems there is practically no difference between the results of the average and the optimal level versions of MCDF calculations, we believe that our average level predictions of ionization energies and oscillator strengths for states with total angular numberJ=0 andJ=1 are of comparable quality to those that could be obtained with an optimal level scheme.