Journal of Chemical Physics vol:113 issue:21 pages:9706-9713
We have implemented dynamic linear and second-order nonlinear light scattering with femtosecond laser pulses. The periodical structure of the impinging light itself does not impede the measurement for intensity correlation times longer than the pulse-to-pulse period. However, the inherently large spectral bandwidth of femtosecond pulses considerably reduces the amplitude of the autocorrelation function. Reducing the coherence volume to increase this amplitude results in a lower count rate. The low efficiency of the second-order nonlinear light scattering, possible relaxation oscillation in solid-state femtosecond lasers, and its quadratic amplification in second-order nonlinear scattering have pronounced influence on the autocorrelation function. Finally, typical relaxation times expected for the dynamics associated with large fluctuations in second-order nonlinearity put a severe limit on the applicability of quasielastic nonlinear light scattering for the study of chemical reaction dynamics. (C) 2000 American Institute of Physics. [S0021-9606(00)51045-9].