Low Even Configurations in the First Spectrum of Rhenium (Re i)

The theory of intermediate coupling with configuration interaction is used to calculate energy levels and $g$ values in the $5d^{5}6s^2$ and $5d^{6}6s$ configurations of Re i. Fifty-one observed levels are fitted with a mean deviation of ±325 ${\mathrm{cm}}^{-1\mathrm{}}$ by using eleven free parameters. The $L(L+1\mathrm{})\mathrm{}$ correction is important, as the mean deviation is ±514 ${\mathrm{cm}}^{-1\mathrm{}}$ without it; the parameter for this correction ($\alpha =66.8\mathrm{}\pm 13$) has a value similar to that in first and second long-period spectra. Standard deviations of the parameters are calculated, and within the limits so defined, Slater's parameters are consistent with expectations based on known behavior in first and second long-period spectra. Calculated $g$ values agree with observed values for thirty-seven levels to about ±0.03. Levels not previously assigned from experiment are given designations; the eigenvectors are used to illustrate qualitative features of these designations.