Fluorescence lifetimes of individual vibronic levels of partially deuterated benzenes: a further test of the theory of radiationless processes

This paper reports experimental studies of the nonradiative lifetimes of individual vibronic levels of several partially deuterated benzenes. The different deuterated species transform according to different symmetries, and therefore the number of totally symmetric modes differs from molecule to molecule. The observed rates of nonradiative decay fall into a regular pattern as a function of increasing deuteration. This observation, together with theoretical arguments, suggests that the accepting modes are, to a good approximation, local modes. Comparison of the predicted relative nonradiative rates with those observed is generally good, but not as accurate as for C6H6 and C6D6. The likely source of the discrepancy is discussed.