Photothermal spectroscopy with pulsed laser sources is developing into a powerful method for determining nonradiative, excited-state quantum yields and decay kinetics of photoexcited molecules in solution. The measurement is an example of photocalorimetry where the heat given off by the decay of excited states and/ or photoproducts is observed as an increase in sample temperature. Photoacoustic spectroscopy with a pulsed laser and a high-bandwidth piezo-electric transducer allows the time dependence of the heat release from excited states to be measured directly with submicrosecond time resolution. The instrument signature on the heat signal for this method, however, is not ideal for determining the photoreaction kinetics of the sample owing to acoustic resonances and lack of any low-frequency response.

© 1991 Optical Society of America

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