Time-resolved hyper-Rayleigh scattering experiments using a femtosecond mode-locked Ti-sapphire laser are presented. The technique is capable of discriminating between hyper-Rayleigh scattered light and fluorescent emission induced by multiphoton absorption with a time resolution of 80 ps. Measurements on the non-fluorescent organic molecules crystal violet and calix- arene demonstrate that the technique can measure first hyperpolarizabilities beta consistent with experiments using a Q-switched Nd:YAG laser. The first hyperpolarizability beta of a fluorescent molecule, which is often overestimated when using a nanosecond laser system, can be corrected for long-term fluorescence using the time-resolved technique as is demonstrated for the octupolar molecule 1,3,5-tris[(4- pyridyl)ethynyl]benzene.
Noordman, O. F. J., Noordman, O. F. J., & van Hulst, N. F. (1996). Time-resolved hyper-Rayleigh scattering:measuring first hyperpolarizabilities Beta of fluorescent molecules. Chemical physics letters, 253(253), 145-150. https://doi.org/10.1016/0009-2614(96)00218-7