A Study of 5p Excitation in Atomic Barium I. The 5p Absorption Spectra of Ba I, Cs I and Related Elements

TLDR: In this paper, an attempt has been made to analyse the limit structure by comparison with the data for Cs I and Hartree-Fock atomic structure calculations and the results obtained are consistent with previous interpretations of the double ionization anomaly in Ba I.

Abstract: New observations of the 5p spectra of Cs I and Ba I are reported. The extreme complexity of the structure does not permit precise configuration labels to be attached to all the excited levels. Nevertheless, more than 160 transitions in Ba I have been ordered into 14 series converging on experimentally known levels of the parent ion. An attempt has been made to analyse the limit structure by comparison with the data for Cs I and Hartree-Fock atomic structure calculations. The results obtained are consistent with previous interpretations of the double ionization anomaly in Ba I. Further comments are made on the comparison between experiment and the predictions of the r.p.a.e. theory for 5p excitation in Ba I. It is shown that the 5p$^{6}$ 6s $^{2}$S$\_{\frac{1}{2}}\rightarrow $ 5p$^{5}$ 6s$^{2}$ $^{2}$P$\_{\frac{1}{2}}$ and $^{2}$P$_{\frac{3}{2}}$ transitions of Cs I have been incorrectly identified and new assignments are proposed.