A Novel Combined Pulsed Laser Flash Photolysis-Optoacoustic Spectroscopy Technique for the Quantitative Study of Relaxation Processes of Excited Species Produced in Two-Laser, Two-Photon Experiments

Article abstract of DOI:10.1021/j100354a024

A novel combination of the established techniques of laser flash photolysis and optoacoustic calorimetry was used as a means for quantitative investigation of relaxation mechanisms in two-laser, two-photon excited species.Flash photolysis was used to determine the absorbance of the initially formed intermediate at the wavelegth and exact time of the second laser pulse.The amplitudes of the optoacoustic signals due to heat emission from the excited intermediate following the second pulse were plotted as a function of the fraction of absorbed photons or of the laser energy.The slope of such a plot for the excited diphenylmethyl radical in cyclohexane was compared to that of a two-laser, two-photon reference system (1-(chloromethyl)naphthalene in cyclohexane) where the excited intermediate (1-naphthylmethyl radical) releases all its absorbed energy rapidly by nonradiative means.From such measurements, the quantum yield of fluorescence of the excited diphenylmethyl radical in cyclohexane was calculated to be 0.31.Other possible applications of the technique are discussed.