Two-photon properties of the La and Lb bands of substituted benzenes computed from CNDO/S

Two-photon tensor invariants proportional to two-photon absorptivities are calculated from CNDO/S CI wavefunctions for a variety of substituted benzenes for transitions to the two lowest singlet states, L_b^? (B_2u^?) and L₃⁺ (B_1u⁺). Providing hexagonal geometry is used, the results demonstrate considerable effectiveness by this method for predicting the relative sensitivity of these bands to vibronic, inductive and conjugative effects, including the intensity ratios for multiple substitutions by aza, methyl and amino. The method fails for fluorobenzene.