Thumbnail
Access Restriction
Open

Author Gonzalez, C. ♦ Theisen, J. ♦ Zhu, Ling ♦ Schlegel, H. B. ♦ Hase, W. L. ♦ Kaiser, E. W.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword 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 ♦ Radiation Chemistry
Abstract 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.
ISSN 00223654
Educational Use Research
Learning Resource Type Article
Publisher Date 1991-09-05
Publisher Place United States
Journal Journal of Physical Chemistry
Volume Number 95
Issue Number 18


Open content in new tab

   Open content in new tab