INTERROGATION AND CONTROL OF CONDENSED-PHASE CHEMICAL-DYNAMICS WITH LINEARLY CHIRPED PULSES - I-2 IN SOLID KR

The effect of linearly chirped pulses in condensed phase ultrafast pum p-probe experiments is investigated by classical simulations for the m odel system of I-2 isolated in a Kr matrix. The central frequency of t he probe laser is selected to monitor exclusively the event of first c ollision and recoil of atoms from the host cage. It is shown that a ch irped probe pulse enables characterization of the magnitude and sign o f the momentum of the evolving trajectory flux. This can be understood by transforming the frequency-time profile of the probe pulse to coor dinate-time space, and noting that the observable signal is a function of the relative group velocities of the traveling wave packet and the traveling window function. The effect of the pump pulse chirp, is a m easure of the controllability of the evolving dynamics. In the particu lar case studied, breaking and remaking of the I-2 bond near the disso ciation limit of the bare molecule, it is shown that the memory of the system outlasts the collision with the cage. Negatively chirped pulse s produce a more tightly focused wave packet during recoil, leading to a stronger population coherence in the subsequent dynamics. (C) 1996 American Institute of Physics.