CONTROL OF CHEMICAL-REACTION PATHWAYS BY FEMTOSECOND PONDEROMOTIVE FORCES - TIME-RESOLVED MULTIPHOTON IONIZATION SPECTROSCOPY STUDY OF OCIOPHOTODISSOCIATION

Femtosecond time-resolved multiphoton ionization spectroscopy is appli ed to the study of the photodissociation of OClO. The observed ratio o f O-2(+)/ClO+ signal increases 12-fold with a 3-fold increase of the p ump laser intensity. They are attributed to the change in the branchin g ratio between the two independent reaction channels leading to Cl+O- 2 and ClO+O, respectively. We believe this is the first,experimental;d emonstration of laser controlled chemical reactions by femtosecond pon deromotive forces. At low pump power, the photodissociation dynamics a t 386 nm is shown to be a two-step process, with the OClO slowly appro aching (time constant 4.6 ps) a transition state that falls apart rapi dly (time constant 250 fs). (C) 1997 American Institute of Physics.