Molecular hyperpolarizabilities of retinal derivatives

We report measurements of the third-order optical susceptibilities of 13-ci s and all-trans retinal derivatives in chloroform liquid solutions using th e Z scan and the optical Kerr gate techniques, with laser pulses of 70 ps a nd 60 fs, at 532 and 800 nm, respectively. The corresponding second hyperpo larizabilities of those molecules are estimated and the results compared to those obtained from semiempirical time-dependent Hartree-Fock calculations . The observed trends for the values of the nonlinear response are explaine d in terms of the pi electron delocalization along the polyenic chain of th e molecules. (C) 1999 American Institute of Physics. [S0021-9606(99)50435-2 ].