Kinetics of the reaction between OH and HO sub 2 on the singlet potential energy surface

Journal Article · Thu Sep 05 00:00:00 EDT 1991 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100171a010· OSTI ID:5259226

Gonzalez, C; Theisen, J; Zhu, Ling; Schlegel, H B; Hase, W L ^[1]; Kaiser, E W ^[2]

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1. Wayne State Univ., Detroit, MI (United States)
2. Ford Motor Co., Dearborn, MI (United States)

Electronic structure calculations at the HF, MP2, and MP4 levels of theory, with the 6-31G** basis set, are reported for stationary points on the OH + HO{sub 2} singlet potential energy surface. Two particularly important stationary points are the trioxide (H{sub 2}O{sub 3}) global minimum and the reaction transition state for O{sub 2}({sup 1}{Delta}) + H{sub 2}O formation. For the latter, the MP4 0 K barrier height is 15.2 kcal/mol. Thus, the formation of O{sub 2}({sup 1}{Delta}) and H{sub 2}O is predicted to be unimportant, except at highly elevated temperatures. MP2 vibrational frequencies calculated for H{sub 2}O{sub 3} are in good agreement with the experiment. Reaction rate theory calculations are performed to assess the effect collisional stabilization of the vibrationally/rotationally excited intermediate H{sub 2}O{sub 3}* has on the apparent loss of the OH and HO{sub 2} reactants. In the high-pressure limit each of the H{sub 2}O{sub 3}* intermediates is collisionally stabilized. However, at intermediate pressures the importance of collisional stabilization depends on the OH + HO{sub 2} {yields} H{sub 2}O{sub 3} reaction exothermicity. The MP4 calculations reported here and a previous configuration interaction (CI) calculation place this exothermicity at {minus}22 to {minus}29 kcal/mol at 0 K. With use of these energies, the collisional stabilization of H{sub 2}O{sub 3}* at room temperature is predicted to become important only at pressures of an inefficient bath gas like He, the loss of the OH and HO{sub 2} reactants is predicted to occur only on the triplet potential energy surface.

• OSTI ID: 5259226
• Journal Information: Journal of Physical Chemistry; (United States), Vol. 95:18; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
HYDROXYL RADICALS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
ELECTRONIC STRUCTURE
ENERGY LEVELS
MOLECULAR STRUCTURE
MOLECULE-MOLECULE COLLISIONS
POTENTIAL ENERGY
PRESSURE EFFECTS
RADICALS
THEORETICAL DATA
THERMODYNAMICS
VIBRATIONAL STATES
COLLISIONS
DATA
ENERGY
EXCITED STATES
INFORMATION
KINETICS
MOLECULE COLLISIONS
NUMERICAL DATA
REACTION KINETICS
400600* - Radiation Chemistry