FEMTOSECOND PHOTODISSOCIATION DYNAMICS OF I-2 STUDIED BY ION IMAGING

Ion imaging is employed to analyze the fragments from timed Coulomb ex plosion studies of femtosecond (fs) molecular dynamics. The technique provides high detection efficiency and direct recording of the two-dim ensional velocity of all ionized fragments. We illustrate the approach by studying photodissociation of iodine initiated by a weak femtoseco nd pump pulse and probed by an intense, delayed femtosecond pulse. The ion images, recorded as a function of the pump-probe delay, reveal th e evolution of the internuclear separation of the dissociating I-2 mol ecule. The experimental results are in good agreement with quantum mec hanical wave packet simulations. We discuss the perspectives for exten ding the studies to photochemical reactions of small polyatomic molecu les. (C) 1998 American Institute of Physics. [S0021-9606(98)01544-X].