Measurements of the hyperpolarizability tensor by means of hyper-Rayleigh scattering

V. Ostroverkhov, R. G. Petschek, K. D. Singer, L. Sukhomlinova, R. J. Twieg, S.-X. Wang, L. C. Chien
2000 Journal of the Optical Society of America. B, Optical physics  
We have designed a hyper-Rayleigh scattering scheme to measure six scalar invariants of the squared hyperpolarizability tensor ␤ 2 . Our theoretical approach expresses the rotational invariants of the irreducible ␤ components as scalars, which eliminates the need for difficult frame transformations. We applied our scheme to several conjugated chiral molecules and found that there are significant Kleinman-disallowed pseudotensor contributions to their hyperpolarizability. These components, along
more » ... e components, along with a large optical rotation and the results of quantum-chemical calculations, indicate a handed nonplanar delocalization of the charge-transfer system in such molecules as predicted by quantum-chemical calculations and are expected to lead to macroscopic second-harmonic generation in axially aligned polymer materials. Pseudotensor contributions to the hyperpolarizability in chiral molecules were found to be as large as the vector contribution in p-nitroaniline. We qualitatively investigated the dispersion in the Kleinman-disallowed components and confirmed that these components are smaller at longer wavelengths. These representation terms are neither fully symmetric nor antisymmetric, so the mixed representation is Hubbard et al. Vol. 15, No.
doi:10.1364/josab.17.001531 fatcat:ogr6jelrwvdlxdn5lwsfz5bixa