Heavy-atom effect on second hyperpolarizabilities of thiophene homologues investigated by a femtosecond optical-Kerr-effect experiment and ab initio molecular orbital calculation

摘要

The second hyperpolarizabilities of three heterocyclic molecules of C4H4X, where X = O (furan), S (thiophene), or Se (selenophene), were investigated by an optical-heterodyne-detected optical-Kerr-effect experiment and an ab initio Hartree-Fock molecular orbital calculation with largely augmented basis sets. From the observed third-order responses the electronic hyperpolarizabilities were determined after the nuclear nonlinear optical responses were removed by Fourier-transform analysis. Results of both experiment and calculation exhibited similar to 2 times enhancement when the heteroatom of O was replaced by Se. The origin of the enhancement and the contribution of the heteroatom to the hyperpolarizability are discussed. Also, a direct comparison of the experimental values with calculated ones is made. (C) 1998 Optical Society of America. [References: 29]