Sodium-Like Spectra of Potassium, Calcium and Scandium

Further identifications have been made in the sodium-like spectra of K, Ca and Sc. The constant second difference law has been used for some time in the analysis of spectra of isoelectronic ions. It is shown that this second difference can be calculated readily, and that to a first approximation it depends only on the total quantum numbers of the initial and final states. Correspondence between calculated and observed second differences is shown for several transitions. Application of the law to ionization potentials is indicated.