Near-Thermal Reactions of Au+(1S,3D) with CH3X (X = F,Cl)

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• 作者：William S. Taylor ; Cullen C. Matthews ; Ashley J. Hicks ; Kendall G. Fancher ; Li Chen Chen
• 刊名：The Journal of Physical Chemistry A
• 出版年：2012
• 出版时间：January 26, 2012
• 年：2012
• 卷：116
• 期：3
• 页码：943-951
• 全文大小：414K
• 年卷期：v.116,no.3(January 26, 2012)
• ISSN：1520-5215

文摘

Reactions of Au⁺(¹S) and Au⁺(³D) with CH₃F and CH₃Cl have been carried out in a drift cell in He at a pressure of 3.5 Torr at both room temperature and reduced temperatures in order to explore the influence of the electronic state of the metal on reaction outcomes. State-specific product channels and overall two-body rate constants were identified using electronic state chromatography. These results indicate that Au⁺(¹S) reacts to yield an association product in addition to AuCH₂⁺ in parallel steps with both neutrals. Product distributions for association vs HX elimination were determined to be 79% association/21% HX elimination for X = F and 50% association/50% HX elimination when X = Cl. Reaction of Au⁺(³D) with CH₃F also results in HF elimination, which in this case is thought to produce ³AuCH₂⁺. With CH₃Cl, Au⁺(³D) reacts to form AuCH₃⁺ and CH₃Cl⁺ in parallel steps. An additional product channel initiated by Au⁺(³D) is also observed with both methyl halides, which yields CH₂X⁺ as a higher-order product. Kinetic measurements indicate that the reaction efficiency for both Au⁺ states is significantly greater with CH₃Cl than with CH₃F. The observed two-body rate constant for depletion of Au⁺(¹S) by CH₃F represents less than 5% of the limiting rate constant predicted by the average dipole orientation model (ADO) at room temperature and 226 K, whereas CH₃Cl reacts with Au⁺(¹S) at the ADO limit at both room temperature and 218 K. Rate constants for depletion of Au⁺(³D) by CH₃F and CH₃Cl were measured at 226 and 218 K respectively, and indicate that Au⁺(³D) is consumed at approximately 2% of the ADO limit by CH₃F and 69% of the ADO limit by CH₃Cl. Product formation and overall efficiency for all four reactions are consistent with previous experimental results and available theoretical models.