Computational model to predict two-photon absorption resonances

A model for calculating two-photon absorption intensities in conjugated systems is presented. The semi-empirical package AM1 is used to generate energies and transition moments via a configuration interaction involving single and double excitations. The evaluation of two-photon absorption cross-section data is carried out by the sum-over-states approach. The linewidth parameters associated with the inhomogeneous-broadening effects are estimated from the one-photon absorption cross-section data. The model is then illustrated by applications to some organic systems. (C) 1997 Optical Society of America.