Simultaneous Determination of Photoreaction Dynamics and Energetics Using Pulsed, Time-Resolved Photoacoustic Calorimetry

Article abstract of DOI:10.1021/ja00312a007

Pulsed, time-resolved photoacoustic calorimetry has been expanded to allow the simultaneous determination of the dynamics and energetics of photoinitiated reactions.Up to three decays may be analyzed assuming either simultaneous or sequential first-order kinetics.With the present experimental apparatus employing a 1 MHz transducer, transient lifetimes fromca. 50 ns to ca. 50 μs may be resolved.Energetics are computed from the fraction of the photon energy released thermally by the decay of the transient of interest.The technique has been applied to the quenching of the benzophenone triplet state by 2,5-dimethylhexa-2,4-diene and the Norris type II photocleavage of valerophenone, giving kinetic and thermodynamic results in excellent agreement with literature values.