ON THE SECONDLY QUANTIZED THEORY OF THE MANY-ELECTRON ATOM

The traditional theory of many-electron atoms and ions is based on the coefficients of fractional parentage and matrix elements of tensorial operators. composed of unit tensors. The calculation of spin-angular coefficients of radial integrals appearing in the expressions of matri x elements of arbitrary physical operators of atomic quantities has tw o main disadvantages: (i) the numerical codes for the calculation of s pin-angular coefficients are usually very time consuming; (ii) f-shell s are often omitted from programs for matrix element calculations sinc e the tables for their coefficients of fractional parentage are very e xtensive. The authors assume that a series of difficulties persisting in the traditional approach to the calculation of spin-angular parts o f matrix elements can be avoided by using this secondly quantized meth odology, based on angular momentum theory, on the concept of the irred ucible tensorial sets, on a generalized graphical method, on quasispin and on the reduced coefficients of fractional parentage.