The results of three different methods of calculation are compared, with extrapolation and fitting of observational data, to obtain values for the energy levels and intervals of the 2<i>s</i><sup><i>r</i></sup> 2<i>p</i><sup><i>k</i></sup> configurations for the elements from sulfur to scandium. Some auxiliary results are also obtained, such as fine-structure parameters which account well for the observed splittings, and intercombination-line wavelengths of interest for the solar corona.
S. O. Kastner, "Energy levels of 1s22sr2pk configurations in the C I and N I sequences, in S, Cl, Ar, K, Ca," J. Opt. Soc. Am. 63, 738-744 (1973)