Femtosecond multiple-pulse impulsive stimulated Raman scattering spectroscopy

Optical control of elementary molecular motion through impulsive stimulated Raman scattering is enhanced by means of timed sequences of femtosecond pulses that are produced by pulse-shaping techniques. In particular, terahertz-rate trains of femtosecond pulses are used for repetitive impulsive excitation of individual phonon modes in an a-perylene molecular crystal. When the pulse repetition rate is matched to the desired phonon frequency, mode-selective vibrational amplification is achieved. A comparison of data acquired with the transient-grating and the pump-probe experimental geometries reveals the timing dynamics of the induced phonon oscillations with respect to the driving femtosecond pulse sequence. 1