Abstract

The ultrafast dynamics of translations and rotations of molecules in liquids can be studied by means of Rayleigh/Raman-type excitation and probing, using ultrashort, broad-bandwidth optical pulses. The time-resolved optical Kerr effect and transient phase-grating scattering are well-known examples of such techniques, which rely on the third-order nonlinear optical susceptibility of the samples. The experimental result of a phase grating experiment on liquid benzene is shown in Fig. la as the dotted curve. The signal consists of an instantaneous component, resulting from electronic hyper-polarizability, and of delayed component that is due to inertial molecular motion. This motion is usually separated into rapidly damped coherent motion for short delays and diffusive behavior at longer time scales. The Fourier- transform of the coherent part gives the total spectrum of excited coherent motion.

© 1996 Optical Society of America