Photoacoustic spectroscopy and energy relaxation processes in matrix isolated CF3NO

Abstract

The photoacoustic, fluorescence excitation, and absorption spectra in the visible region are compared for CF3NO isolated in argon. Results are related to possible photodissociative and nonradiative decay channels available to the molecule in the S1 excited state. Vibrational relaxation occurs in less than a few nanoseconds in this state and the quantum yield for fluorescence from the v′=0 level is 0.015. Subsequent relaxation is likely to involve internal conversion to the ground state, as in the vapor. In contrast to gas phase results, the matrix data give no indication of a direct, ‘‘second channel,’’ predissocation path near 627 nm. No evidence is seen for transient escape of the CF3 and NO photofragments from the matrix cage and all nonradiative processes appear to be complete in less than one microsecond. The time evolution of the photoacoustic pulse and the detection limits of these matrix measurements are discussed briefly.