Study of the Lifetimes of Individual Vibronic States of the Isolated Benzene Molecule

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Abstract
In this paper we report measurements of the lifetimes of 22 vibronic states of benzene and the relative quantum yields of fluorescence for transitions originating from these states. The measurements, which are all made in the free molecule limit, are used to test the theory of radiationless processes. It is found that the available theory provides a moderately good description of the observations. Our principal observation is that the nonradiative lifetime of the prepared state decreases with increasing excitation over the origin in such a way that the decrement in nonradiative lifetime per quantum of vibrational energy is approximately constant. The excitation of progressions in low frequency out‐of‐plane modes decreases the nonradiative lifetime per unit energy more than do excitations of progressions in, say, the totally symmetric mode. We also discuss the pressure dependence of the lifetime of a prepared state and its relationship to molecular properties.