Accurate Semi-Empirical Formulae for the Energy Structure of Li I-like Spectra

Abstract

By combining all available theoretical and experimental data we first derive expressions for the Z-dependence of the 2p2P splitting and of the resonance transitions 2s2S1/2-2p2P1/2, 3/2, thereby obtaining a check on reported wavelengths of these transitions and on their identification in solar flare spectra. Further, by combining the observed transitions 2p-3d with the 3d ionization energy, calculated on the basis of the polarization concept, we determine the ionization limit for each spectrum and summarize the results in a semi-empirical expression in Z. Finally, Z-dependent coefficients in 3-parameter Ritz formulae are derived for ns2S and np2P, which complete the accurate description of the energy structure of these spectra. Explicit results are tabulated up to Ni XXVI. They give an estimate of the errors in existing measurements and reveal a number of misidentifications in published line lists.