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.