Screening Constants from Optical Data

Grotian identified the relativistic doublets which correspond to the ionization of an $n_2$ shell in the spectra of the rare gases. Similarly the doublets which belong to the $n_3$ shells are found in the spectra of 29 Cu, 45 Rh, and 79 Au. The different relative stability of the $n_3$ electrons as compared with the ${\mathrm{}(n+1\mathrm{})\mathrm{}}_1$ electrons is clearly noticeable in every one of the three long periods. The screening constants are in good agreement with those computed from x-ray data, even in cases where the "optical" screening constant is obtained from elements the outer shell of which is not yet complete.