The vibrational energy redistribution due to the geometrical rearrangement induced by photoexcitation of stilbene-3 into the S, state is monitored selectively with respect to the different forms of nuclear motion in this polyatomic system. The femtosecond time-resolved, pump-CARS scheme is employed to trace the population flow between vibrational modes associated with this structural rearrangement. The decay of the signal at 1189-1333 cm(-1) is attributed to vibrational cooling with population flowing out of these modes, whereas the rise observed at 1600 cm(-1) is attributed to reorganization of the respective bonds due to the transition from the So to the S, state geometry. (c) 2005 Elsevier B.V. All rights reserved.