Redistribution and relaxation of vibrational excitation of CH-stretching modes in 1,1-dichloroethylene and 1,1,1-trichloroethane

Anti-Stokes Raman scattering after resonant infrared excitation with femtos econd light pulses was used to monitor the vibrational excitation of the CH -stretching modes of liquid CH2CCl2 and CH3CCl3, Selective excitation and p robing allowed determination of the various time-constants for the redistri bution between the CH-stretching modes and their relaxation. For the symmet ric CH-stretching mode of CH2CCl2 relaxation times of 3.5 and 9.5 ps are de termined for the transfer to overtones and to the asymmetric CH-stretching mode, respectively. For CH3CCl3 these time constants are 5.0 and 4.7 ps.