Photoinitiated processes in complexes: subpicosecond studies of CO2—Hl and stereospecificity in Ar—HX

Abstract

Build-up times for the OH product of photoinduced reactions in CO2—HI complexes were measured for the photolysis wavelength range 235–263 nm by using the subpicosecond resolution pump–probe method pioneered by Zewail and co-workers. There is reasonable accord with theory and recent results from crossed-molecular-beams experiments. To illustrate the squeezed-atom effect, complementary measurements of hydrogen atom translational-energy distributions were carried out by using the high resolution high-n Rydberg time-of-flight (HRTOF) method of Welge and co-workers. Prototypical cases of Ar—HBr and Ar—HI complexes are reported. The former illustrates the squeezed-atom effect or caging of the exiting hydrogen. The latter is dominated by the formation of radical–molecule complexes. Extensions to other radical–molecule complexes are discussed.