NONSTATISTICAL CO PRODUCT DISTRIBUTIONS FROM THE HOT H-ATOM REACTION, H+CO2-]OH+CO

The hot H-atom reaction, H + CO2-->OH + CO is investigated under several initial conditions designed to vary the angular momentum of the CO2 reactant. The translationally hot H atoms are produced by photodissociating H2S at 193 nm, resulting in a reaction exoergicity of approximately 120 kJ mol-1. The internal energy in the CO product is monitored by laser-induced fluorescence in the VUV spectral range. Under near-nascent conditions we report the rotational distributions of CO in upsilon" = 0 under CO2 reactant "temperatures" of 300, 70 and 40 K. Also reported are the rotational distributions of CO in upsilon" = 1 at 300 K and 70 K and the population ratios of [upsilon" = 1]/[upsilon" = 0] at both initial CO2 temperatures. Three distinctively "dynamical" aspects of the potential energy (PE) surface are exhibited in this set of experiments: (i) As the CO2 reactant is cooled, a cooling of the CO distribution is seen which suggests the reaction intermediate does not live long enough to randomize its internal energy. (ii) We report a coupling of vibrational and rotational excitation in the CO product indicated by a "hotter" rotational energy in upsilon" = 1 than upsilon" = 0 at 300 K. (iii) In addition, we report different [upsilon" = 1]/[upsilon" = 0] ratios at the two CO2 initial temperatures. Contrary to nearly all indications from measurements on the OH product, the CO product is rich in "nonstatistical" behavior.