APPLICATIONS OF PHOTOTHERMAL BEAM DEFLECTION CALORIMETRY TO ORGANIC-PHOTOCHEMISTRY

Photothermal beam deflection calorimetry (PDC) measures the time-depen dent heat release that follows optical excitation of a sample. From th ese measurements, parameters such as reaction enthalpies and rates can be determined. In this work, it is shown that this method can be conv eniently applied to the measurement of intersystem crossing quantum yi elds, triplet energies and photochemical reaction enthalpy changes in a variety of organic molecules. In general, PDC signals are linear wit h excitation energy and sample concentration. Also, the rates and enth alpies derived from these measurements show good agreement with litera ture values. In certain cases, a non-linear response of the signal wit h respect to the excitation energy is observed. This appears to be the result of multiphoton absorption by the sample. Comparison of PDC wit h complementary photothermal methods, such as photoacoustic calorimetr y and thermal lens calorimetry, is discussed.