FEMTOSECOND, VELOCITY-GATING OF COMPLEX STRUCTURES IN SOLVENT CAGES

The method of femtosecond velocity-gating in complex systems is report ed with an application to the caging problem in a pure solvent cluster of iodobenzenes (n = 2-8). Two structural forms of iodine atoms in th e clusters are identified based on the two distinct product recoil vel ocity distributions and their temporal behaviors: One is the ''uncaged '' iodine atoms that exhibit ultrafast dissociations (similar to 1.4 p s) and high recoil velocities; the other is the ''caged'' iodine atoms that escape very slowly (up to 300 ps) from the clusters with very lo w kinetic energies. These solvation dynamics relate to the nature of t he microscopic molecular structures.