The use of CNDO in spectroscopy. XV. Two photon absorption

Abstract
Two−photon absorptivities have been calculated within the CNDO/S‐CI molecular orbital framework of Del Bene and Jaffé utilizing the second order time dependent perturbation equations of Göppert–Mayer and polarization methods of McClain. Good agreement is found between this theory and experiment for transition energies, symmetries, and two‐photon absorptivities for the following molecules: biphenyl, terphenyl, 2,2′‐difluorobiphenyl, 2,2′‐bipyridyl, phenanthrene, and the isoelectronic series: fluorene, carbazole, dibenzofuran.