A theoretical study of the npk configurations

An up-to-date picture of the known np² and np³ configurations is presented by plotting the reduced energy ? against ψ = ξ_p/(5F₂ + ξ_p) according to Edlén. It is concluded that the p² level values of S XI, Sc XVI, Ti XVII, V XVIII, Ni XV and Te III, and the p³ level values of Al VII, Si VIII, P IX, Cl X, Se II and Xe IV need to be improved. Edlén's (1972) work on n = 2 and Svensson's (1971) work on n = 3 give a very satisfactory fit to our ψ-? graphs. The (F₂ - ξ_p) V_sψ graphs enable us to study coupling variations along the same and different isoelectronic sequences.The Z-dependence of the ground intervals 4s² 4p⁴ have been studied theoretically for the first time. The level values are represented, within less than 0.2% error, by semi-empirical formulae having 3–5 adjusted parameters and are based on data obtained from laboratory observations. The results provide means for checking laboratory and astrophycial identifications and measurements.