MEASUREMENT OF FIRST HYPERPOLARIZABILITIES BY HYPER-RAYLEIGH SCATTERING

The origin of spurious and irreproducible signals in the measurement o f the hyper-Rayleigh scattering (HRS) of solutions is investigated. A new cell design, coupled with continuous solution filtration through a 20 nm filter, is shown to improve the reproducibility of the measurem ent to +/-5%. A transverse cell dimension of similar to 2 mm reduces a bsorption of the second harmonic. A simple monochromaticity test is us ed to identify luminescence, and we recommend that it is made routinel y. Scattering from the [Ru(bipy)(3)](2+) cation, attributed to HRS by Zyss et al. [Chem. Phys. Lett. 206, 409 (1993)], appears to be largely due to two-photon excited luminescence. The reliability of calibratio n procedures is examined, and some revised hyperpolarizabilities are r eported. (C) 1996 American Institute of Physics.