QUANTUM CONTROL OF I-2 IN THE GAS-PHASE AND IN CONDENSED-PHASE SOLID KR MATRIX

We present experimental results and theoretical simulations for an exa mple of quantum control in both gas and condensed phase environments. Specifically, we show that the natural spreading of vibrational wavepa ckets in anharmonic potentials can be counteracted when the wavepacket s an prepared with properly tailored ultrafast light pulses, both for gas phase I-2 and for I-2 embedded in a cold Kr matrix. We use laser i nduced fluorescence to probe the evolution of the shaped wavepacket. I n the gas phase, at 313 K, we show that molecular rotations play an im portant role in determining the localization of the prepared superposi tion. In the simulations, the role of rotations is taken into account using both exact quantum dynamics and nearly classical theory. For the condensed phase, since the dimensionality of the system precludes exa ct quantum simulations, nearly classical theory is used to model the p rocess and to interpret the data. Both numerical simulations and exper imental results indicate that a properly tailored ultrafast light fiel d can create a localized vibrational wavepacket which persists signifi cantly longer than that from a general non-optimal ultrafast Light fie ld. The results show that, under suitable conditions, quantum control of vibrational motion is indeed possible in condensed media. Such cont rol of vibrational localization may then provide the basis for control ling the outcome of chemical reactions. (C) 1997 American Institute of Physics.