Experimental and Computational Study of the Gas-Phase Reaction of O(1D) Atoms with VF5

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• 作者：Asylkhan A. Rakhymzhan ; Alexey I. Chichinin ; Vitaly G. Kiselev ; Nina P. Gritsan
• 刊名：The Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：February 7, 2013
• 年：2013
• 卷：117
• 期：5
• 页码：814-820
• 全文大小：358K
• 年卷期：v.117,no.5(February 7, 2013)
• ISSN：1520-5215

文摘

The reactions of O(p>1p>D) atoms with VF₅ at room temperature have been studied by time-resolved laser magnetic resonance at the buffer gas (SF₆) pressure of 6 Torr. The O(p>1p>D) atoms were produced by the photodissociation of ozone using an excimer laser (KrF, 248 nm). By monitoring the kinetics of FO radical formation, the bimolecular rate constant of O(p>1p>D) consumption in collisions with VF₅ has been determined to be k_VF5 = (7.5 卤 2.2) 脳 10p>鈥?1p> cmp>3p> sp>鈥?p>. The branching ratio for the channel producing FO radicals (k_8a) has been found to be k_8a/k_VF5 = 0.11 卤 0.02. Quantum chemical calculations at the CCSD(T)/CBS level of theory give evidence that the reactions of O(p>1p>D) with VF₅ proceed via the VF₄OF intermediate. The enthalpy of the reaction leading to this intermediate formation was calculated to be 鈭?45.8 kJ/mol. In qualitative agreement with the experimental results, the reaction channel O(p>1p>D) + VF₅ 鈫?FO + VF₄ (8a) turned out to be 72.9 kJ/mol energetically more favorable than the channel O(p>1p>D) + VF₅ 鈫?F + OVF₄ (8b). The dissociation enthalpy of the OVF₄ radical was calculated to be very low (18.1 kJ/mol); hence, the decay of OVF₄ to F + OVF₃ should proceed very fast. The molecular channel O(p>1p>D) + VF₅ 鈫?F₂ + VF₃O, though being most favorable thermodynamically, is kinetically unimportant.