Closure Procedure for Two-Photon Absorption Intensities
Thomas Roy Stoner, John B. Gruber · The Journal of Chemical Physics · 1970
A derivation of a sum identity is presented which is an extension of the Thomas–Reiche–Kuhn sum rule for oscillator strengths. A derivation of the probability amplitude for two-photon absorption by a one-electron quantum system is sketched, and an application for the sum identity is suggested in the approximate evaluation of the perturbation sum which appears in the expression for the amplitude.