Calculation of excited molecular states taking account of partial relaxation of the core

Effects of electron-core relaxation in the excitation of atomic systems are considered. A new approach to the consideration of relaxation is proposed, and the corresponding equations are obtained. In the π-electron approximation, the first excited states of some organic molecules are calculated by the V(N−1)-potential method, the Morokuma-Iwata method, and a method proposed in the present work.