Measurement of small absorptions in liquids

We use the recently developed technique of pulsed dye-laser optoacoustic spectroscopy of liquids to study the weak 607-nm absorption band of benzene dissolved in various concentrations in CCl(4). The technique involves the use of submersed piezoelectric transducer and gated detection of the transient acoustic signal. With increasing dilution, the peak of the 607-nm band is observed to be more blue-shifted, and the linewidth and asymmetry of the band decrease. We verify that the present technique can detect absorption coefficients of 10(-6) cm(-1) and absorbed energy of 10(-9) J. With these high sensitivities, we show that nonlinear optical processes such as multiphoton absorption and stimulated Raman scattering in liquids should be readily observable with our optoacoustic method.