Photoionization of Se2+ and S4+ ions using the screening constant per unit nuclear charge method

Abstract

Photoionization of Se2+ and S4+ ions are studied in this paper. Accurate resonance energies and quantum defects of the 4s4p2 (3P2, 1D2) 4 s → 4s4p2(2D5/2)np, and 4s24p (3P1, 3P2,1D2) 4p → 4s24p(2P3/2)nd Rydberg transitions in Se2+ are reported. In addition precise energies and quantum defects belonging to the resonances arising from 2p → nd (1P1, 3D1) and 2p → ns (1P1, 3D1) excitations in ground state (1S0) S4+ and to the 1s22s22p63s2 1S0 → 1s22s2p63s2np 1P1 transitions in S4+are tabulated. Calculations are performed in the framework of the Screening constant per unit nuclear charge (SCUNC) method. The SCUNC semi-empirical formulas reproduce excellently the existing synchrotron radiation measurements on Se2+ [Esteves et al., 2015. Phys. Rev. A. 92, 063424]. Furthermore, the present results agree excellently with the synchrotron measurements and MCDF and R-matrix calculations on S4+ [Mosnier et al., 2022. Phys. Rev. A. 106, 033113]. The new SCUNC data tabulated up to n = 50 may be useful reference data suitable for incorporation into astrophysical modeling codes.