STATE-TO-STATE COLLISIONAL VIBRATIONAL-ENERGY TRANSFER IN S1 P-DIFLUOROBENZENE

State-to-state vibrational energy transfer from six levels in S1 p-dif luorobenzene (pDFB) vapor at 300 K has been studied for single collisi ons with argon atoms. The levels range in vibrational energy up to 818 cm-1 and involve quanta of nu5, nu6, nu8, and nu30. This investigatio n is a continuation of a previous study concerning the zero-point leve l. The study is based on a laser pump-dispersed fluorescence detection method that monitors all significant one-collision channels from a gi ven initial state. In common with results from other studies of polyat omic vibrational energy transfer, large state-to-state rate constants (up to 0.2 times hard sphere) are observed with high selectivity among possible final states. Among the 30 modes of pDFB, processes with sma ll quantum changes in the two lowest-frequency modes, nu8 and nu30, do minate the energy transfer. Transfer to nearly resonant levels is gene rally too inefficient to observe. The rate constants for gaining or lo sing quanta of nu8 and of nu30 are insensitive to the vibrational iden tity of the initial state. The collisional flow patterns from each lev el are semiquantitatively described by a previously developed treatmen t of the SSH-T vibrational energy-transfer model.