Calculation of the optical characteristics of molecules with an open shell of electrons

Abstract

Two variants of nonstationary perturbation theory have been developed for many-electron systems with an open shell. The first variation is bound perturbation theory in the restricted Hartree-Fock method, and the second is perturbation theory in the Tamm-Dankov method. The equations have been formulated in terms of a density matrix in the LCAO approximation. The equations in first-order perturbation theory which permit the calculation of the linear response of a system to an external dynamic perturbation have been considered in detail. The question of the poles of the dynamic polarizability calculated by various methods has been discussed. Calculations of the Cauchy moments and the first poles of the dynamic dipole polarizability of a number of molecules of conjugated open-shell hydrocarbons (radical ions and triplet excited states of even alternant hydrocarbons and doublet states of odd alternant hydrocarbons), as well as tree-electron atomic systems (Li I, Be II, and B III) have been carried out in the framework of both methods.