Application of chirped ultrashort pulses for generating large-amplitude ground-state vibrational coherence: A computer simulation

Computer simulations are presented to show that frequency-chirped ultrashort pulses, when properly employed, may be more effective than their compressed analogs for generating large-amplitude vibrational coherence in molecular systems. A one-dimensional model, which was used previously to simulate impulsive optical excitation of CsI, is used [Chem. Phys. Lett. 158, 238 (1988)]. A negatively chirped pulse (for which the light is redshifted with time) is devised to excite the population initially onto the excited surface. As this population propagates in the repulsive upper state, the later red-shifted portions of the pulse follow the change in the resonance conditions and effectively dump the population back down into excited vibrational states of the ground surface. These results are compared with the dynamics simulated with the compressed and positively chirped analogs, and the experimental realization of this scheme is discussed.