SPECTRAL DISPERSION OF 2ND MOLECULAR HYPERPOLARIZABILITY OF DIACETYLENE DERIVATIVES - CORRELATION WITH ELECTRONIC AND CHEMICAL-STRUCTURE

Dispersion of the second hyperpolarizability gamma(- omega;omega, omeg a, - omega) of a series of conjugated diacetylene derivatives measured by single beam Z-scan technique, is presented. The spectrum of gamma is explained by a three-level model involving a one-photon excited sta te, a two-photon excited state and the ground state. The location of o ne and two-photon states and corresponding transition dipole moments h ave been estimated. The influence of various electronic states on the nonlinear optical properties of these derivatives have been discussed. Broad correlations of the nonlinearity with the structure have been d rawn. (C) 1998 American Institute of Physics.