Control of chemical reaction pathways by femtosecond ponderomotive forces: Time-resolved multiphoton ionization spectroscopy study of OCIO photodissociation

Femtosecond time-resolved multiphoton ionization spectroscopy is applied to the study of the photodissociation of OClO. The observed ratio of O-2(+)/ClO+ signal increases 12-fold with a 3-fold increase of the pump laser intensity. They are attributed to the change in the branching ratio between the two independent reaction channels leading to Cl+O-2 and ClO+O, respectively. We believe this is the first,experimental;demonstration of laser controlled chemical reactions by femtosecond ponderomotive forces. At low pump power, the photodissociation dynamics at 386 nm is shown to be a two-step process, with the OClO slowly approaching (time constant 4.6 ps) a transition state that falls apart rapidly (time constant 250 fs). (C) 1997 American Institute of Physics.