Dynamics of reactions of fast hydrogen atoms
The endothermic reactions of fast (hyperthermal translational energy) hydrogen atoms with O[sub 2], HOD, and D[sub 2]O are investigated in pump-probe experiments under bulk gas, single-collision conditions. The H atoms are generated in the presence of O[sub 2], HOD, or D[sub 2]O by pulsed laser photolysis, of HI. After a short time delay following photolysis, a second laser pulse probes the branching ratios and nascent vibrational, rotational and electronic fine-structure state distributions of the hydroxyl (OH and OD) reaction products by laser induced fluorescence (LIF). The reaction H + O[sub 2] [yields] OH(v, N) + O is investigated experimentally and theoretically at a center-of-mass collision energy of 1.6 eV. Comparison of measured OH vibrational and rotational distributions with those calculated using phase space theory suggests a competition between two reaction mechanism at this collision energy: reaction involving a long-lived complex and direct reaction. The OH A-doublet ratio is found to be 2:1 in the limit of high rotation. This observation is explained using a simple geometric model of the reaction, which is generalized to a large class of reactions of the form A + BC [yields] AB+C. A study of the reaction H + HOD([nu]1, [nu]2, [nu]3) [yields] OH(v, N)(OD(v, N)) + HD(H[sub 2]) is carried out at 1.5 eV collision energy. Bond-specific chemistry is observed for this reaction: excitation of either the OH or OD stretching vibration leads to selective cleavage of the excited bond. Vibrational stretch excitation enhances the reaction cross section much more than would an equivalent amount of additional translational energy, as expected for the H + HOD reaction because it has a late barrier. The effects of polyatomic reagent stretch and bend excitation are compared in a state-to-state study of the reaction H + D[sub 2]O([nu]1, [nu]2, [nu]3) [yields] OD(v, N) + HD. D[sub 2]O stretch excitation enhances the reaction rate, whereas bend excitation does not.
- Research Organization:
- Stanford Univ., CA (United States)
- OSTI ID:
- 7275026
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
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ATOM-MOLECULE COLLISIONS
CHEMICAL REACTION KINETICS
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HYDROXYL RADICALS
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COLLISIONS
ELEMENTS
HYDROGEN COMPOUNDS
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MOLECULE COLLISIONS
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400201* - Chemical & Physicochemical Properties