Initial Reaction Probability and Dynamics of Ozone Collisions with a Vinyl-Terminated Self-Assembled Monolayer

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• 作者：Jessica W. Lu ; Larry R. Fiegland ; Erin Durke Davis ; William A. Alexander ; Alec Wagner ; Richard D. Gandour ; John R. Morris
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：December 29, 2011
• 年：2011
• 卷：115
• 期：51
• 页码：25343-25350
• 全文大小：925K
• 年卷期：v.115,no.51(December 29, 2011)
• ISSN：1932-7455

文摘

The gas鈥搒urface reaction dynamics of ozone with a model unsaturated organic surface have been explored through a series of molecular beam scattering experiments. Well-characterized organic surfaces were reproducibly created by adsorption of C鈺怌-terminated long-chain alkanethiols onto gold, while the incident molecular beams were created by supersonic expansion of ozone seeded in an inert carrier gas to afford control over collision energy. Time-of-flight distributions for the scattered molecules showed near complete thermal accommodation of ozone for incident energies as high as 70 kJ/mol. Reflection鈥揳bsorption infrared spectroscopy, performed in situ with ozone exposure, revealed that oxidation of the double bond depends significantly on the translational energy of O₃. For energies near room temperature, 5 kJ/mol, the initial reaction probability (纬₀) for the formation of the primary ozonide was determined to be 纬₀ = 1.1 脳 10^鈥?. As translational energy increased to 20 kJ/mol, the reaction probability decreased. This behavior, along with a strong inverse relationship between 纬₀ and surface temperature, demonstrates that the room-temperature reaction follows the Langmuir鈥揌inshelwood mechanism, requiring accommodation prior to reaction under nearly all atmospherically relevant conditions. However, measurements show that the dynamics transition to a direct reaction (analogous to the Eley鈥揜ideal mechanism) for elevated translational energies.