Revised and extended analysis of doubly ionized selenium: Se III

Abstract

The spectrum of selenium was recorded on a 3 m normal incidence vacuum spectrograph of the Antigonish laboratory (Canada) in the wavelength region 300–2080 Å using a triggered spark source. The theoretical structure of doubly ionized selenium (Se III) was predicted by Cowan's multi-configuration interaction code. The ground configuration of Se III is 4s24p2 and the excited configurations are of the type 4s24pnd (n⩾4), 4s24pns (n⩾5) and the inner shell excitation gives rise to the 4s4p3 configuration. The 4s24p2−[4s4p3+4s24p (4d+5d+6d+7d+5s+6s+7s+8s)] transition array has been analyzed. Several earlier reported levels have been revised and four new configurations have been added. All the levels of these configurations have been established. More than 180 spectral lines have been identified in this spectrum. A total of 75 energy levels belonging to the above-mentioned configurations have been established. Least-squares fitted parametric and Hartree–Fock calculations were used to interpret the observed spectrum. Excellent agreement with theoretical calculations was noticed. The standard deviation of least-squares fit is only 110 cm−1. The ionization potential of Se III was found to be 255 650±150 cm−1 (31.696±0.018 eV). The accuracy of our wavelengths for sharp lines is better than ±0.005 Å.