CAN CHIRP ENHANCE CUMULATIVE PRE-RESONANT IMPULSIVE STIMULATED RAMAN EXCITATION

Simple arguments are presented and numerical calculations are performe d which show that frequency chirp increases the amplitude of vibration al motion induced in the ground state of I-2 by optimized sequences of ultrashort, pre-resonant optical pulses. Sequences with a variety of constraints on pulse chirp rates and pulse center frequencies were gen erated by time local optimization and are compared. A sequence with pu lse-by-pulse variable chirp and variable center frequency is shown to be considerably more effective than the most effective sequence with a fixed negative chirp rate and constant pulse center frequency, which is in turn much more effective than a sequence of unchirped fixed-cent er-frequency pulses considered previously. The best sequence of pulses induces a 0.4 Angstrom circuit in the expectation value of the I-2 st retch from cumulative pre-resonant impulsive stimulated Raman scatteri ng. (C) 1996 American Institute of Physics.