Nonstationary theory of perturbations for open-shell atoms in the Hartree-Fock approximation

For a multielectron open-shell system exposed to an external time-dependent perturbation, the Hartree-Fock nonstationary equations are obtained in terms of density operators. Using them as a basis, equations of nonstationary "coupled" perturbation theory are suggested in orbital representation within the framework of the two-operator variant of the Roothaan method for an open shell. The perturbation theory corrections to the orbitals have been found in the form of expansions in unperturbed orbitals which are assumed to be calculated in the LCAO approximation in the basis of Slater-type atomic orbitals. The dynamic polarizability of open-shell atoms of substances from Li to F and Sc has been calculated as an even-power series of the frequency of incident radiation.