The Transitions 3s-3p and 3p-3d, and the Ionization Energy in the Na I Iso-electronic Sequence

Abstract

Simple expressions in Z for the fine-structure intervals of 3p ² P and 3d ² D and for the transition energies 3s-3p and 3p-3d are derived from experimental data in the iso-electronic sequence of Na I-like spectra from S VI to Mo XXXII. The formulae provide a check on the accuracy of existing measurements and an easy interpolation of missing data. By a combination of the resulting energy values of 3d ² D _5/2,3/2 with the ionization energies of nf ² F _7/2,5/2, given by a formula based on the polarization concept, the series limits are derived from observations of the transitions 3d-nf. The results are summarized in a semi-empirical expression in Z for the ionization energy valid for Z ⩾ 16. Finally, interpolation formulae are given for the line strengths of the transitions 3s-3p and 3p-3d based on calculations by A. W. Weiss.