Classification of states and determination of wave functions in the case of almost - degenerate configurations

Appropriate unitary groups and their expansions are proposed for classifying states in overlapping configurations of atomic spectra. Overlapping configurations are considered as a single combined configuration. The coefficients of the wave functions of pure configurations are then obtained using only group methods from the properties of the group generators, and do not depend on the energy matrix.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 21–23, March, 1984.