Theoretical studies of two-photon absorption processes. II. Model calculations

Abstract

Two-photon absorption cross sections are calculated for the hydrogen atom and the hydrogen molecule. Three methods of calculation are employed: (1) a second-order time-dependent perturbation expansion; (2) a "mean- energy" approximation; (3) a sum-rule equivalent of perturbation theory. The various methods are compared and evaluated in terms of their general utility in describing double-photon absorption processes.