Improvement in the theoretical determination of the fine structure of terms of atomic species of boron, carbon, and nitrogen type

The state of theoretical determination of the fine structure of light atoms is described. It is shown that the approximation of the two-electron states model must be used when the calculation of the fine structure is refined on the basis of a multiconfiguration approximation. The expression for the matrix elements of spin-dependent interactions is derived for the case of two unfilled shells and specialized for the case where one of the shells is filled. Expressions are found for the interaction matrix elements between two equivalent p, d and f electrons and a filled s shell. The results of determining the fine structure of boron, carbon, and nitrogen are given. Results have been improved by using the multiconfiguration approximation on the basis of the two-electron states model.