Oscillator strengths of some Ba lines; a treatment including core-valence correlation and relativistic effects

Theoretical studies of selected oscillator strengths (f) for Ba are reported in the length formulation using LS-coupled wavefunctions. Insight into the importance of relativistic effects is obtained by performing all-electron non-relativistic calculations with an extended Slater basis set as well as relativistic-core potential calculations with ten electrons treated explicitly in an extended valence Gaussian basis set. Relativistic effects are observed not only to change the spatial extent of the orbitals, but also to alter substantially the configurational character of the wavefunctions. Core-valence correlation is explicitly included within a configuration-interaction treatment. Since there is a synergistic effect between correlations and relativistic effects, both must be included for consistently reliable results. The authors find that the intensity of the intercombination line ( 3 P 1 - 1 S 0 ) is accurately determined by accounting for the deviations from the Lande interval rule provide and accurate measure of the degree of mixing.