Acceleration of the Reaction OH + CO 鈫?H + CO2 by Vibrational Excitation of OH

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• 作者：Nanase Kohno ; Mari Izumi ; Hiroshi Kohguchi ; Katsuyoshi Yamasaki
• 刊名：Journal of Physical Chemistry A
• 出版年：2011
• 出版时间：May 19, 2011
• 年：2011
• 卷：115
• 期：19
• 页码：4867-4873
• 全文大小：885K
• 年卷期：v.115,no.19(May 19, 2011)
• ISSN：1520-5215

文摘

The collision complex formed from a vibrationally excited reactant undergoes redissociation to the reactant, intramolecular vibrational relaxation (randomization of vibrational energy), or chemical reaction to the products. If attractive interaction between the reactants is large, efficient vibrational relaxation in the complex prevents redissociation to the reactants with the initial vibrational energy, and the complex decomposes to the reactants with low vibrational energy or converts to the products. In this paper, we have studied the branching ratios between the intramolecular vibrational relaxation and chemical reaction of an adduct HO(v)鈥揅O formed from OH(X²螤_i) in different vibrational levels v = 0鈥? and CO. OH(v = 0鈥?) generated in a gaseous mixture of O₃/H₂/CO/He irradiated at 266 nm was detected with laser-induced fluorescence (LIF) via the A²危⁺鈥揦²螤_i transition, and H atoms were probed by the two-photon excited LIF technique. From the kinetic analysis of the time-resolved LIF intensities of OH(v) and H, we have found that the intramolecular vibrational relaxation is mainly governed by a single quantum change, HO(v)鈥揅O 鈫?HO(v鈥?)鈥揅O, followed by redissociation to OH(v鈥?) and CO. With the vibrational quantum number v, chemical process from the adduct to H + CO₂ is accelerated, and vibrational relaxation is decelerated. The countertrend is elucidated by the competition between chemical reaction and vibrational relaxation in the adduct HOCO.