Energy levels of singly ionized cesium (CsII)

The system of observed energy levels of CsII of Wheatley and Sawyer has been reinterpreted through the use of Hartree-Fock calculations and published Zeeman effect and hyperfine-structure measurements. Of the 80 known levels, 30 have been rejected as being not real. A revised list of 54 observed levels of CsII is presented that includes the $5p^{5}5d{}_{}{}^1{}_{}{}^{}P_1^{}{}_{}{}^{}$ level recently found by Reader and Epstein and three levels of the $5p^{5}6d$ configuration that were located with the aid of Sommer's line list. Percentage compositions and Slater parameters are given for the $5p^5\mathrm{}(5d+6s)\mathrm{}$, $6p$, and ($6d+7s$) configurations, Severe configuration mixing is found for levels of the $5p^5\mathrm{}(5d+6s)\mathrm{}$ group. The measured $g$ values of the $5p^5\mathrm{}(5d+6s)\mathrm{}$ levels provide evidence of a strong term dependence for the parameter $G^1\mathrm{}\left(5p5d\right)\mathrm{}$. By taking into account displacements of the $5p^5\mathrm{ns}$ levels due to configuration interaction, the ionization energy is revised to be 186 600 ± 150 ${\mathrm{cm}}^{-1\mathrm{}}$ (23.14 ± 0.02 eV).