Vibrational energy transfer and localization in disordered solids by picosecond CARS spectroscopy

摘要

The dephasing rate of the three longest lived vibrons of naphthalenehyphen;h8(T1sim;100 ps) is investigated by picosecond CARS in disordered mixed crystals containing naphthalenehyphen;d8. Vibrational energy transfer can either occur preferentially to one acceptor state or fairly equally to a number of acceptors. For two of the vibrons studied, the decay occurs preferentially to the lower energyd8Nvibron of the same normal coordinate. The other vibron studied appears to couple fairly equally to a large number of acceptors since its correspondingd8Nvibration is higher in energy and unavailable for decay. The coupling matrix elements are calculated for the specific decay routes and found to be sim;10 greater than the coupling to other acceptor states. For one of the vibrations, nonexponential decays are observed at highd8Nconcentrations indicating a distribution of environments and hence localization. A fit to a Voight line shape gives an estimate of the inhomogeneous distribution of frequencies experienced by this localized vibration.