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

Reactions of Au super(+)( super(1)S) and Au super(+)( super(3)D) with CH sub(3)F and CH sub(3)Cl 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 super(+)( super(1)S) reacts to yield an association product in addition to AuCH sub(2) super(+) 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 super(+)( super(3)D) with CH sub(3)F also results in HF elimination, which in this case is thought to produce super(3)AuCH sub(2) super(+). With CH sub(3)Cl, Au super(+)( super(3)D) reacts to form AuCH sub(3) super(+) and CH sub(3)Cl super(+) in parallel steps. An additional product channel initiated by Au super(+)( super(3)D) is also observed with both methyl halides, which yields CH sub(2)X super(+) as a higher-order product. Kinetic measurements indicate that the reaction efficiency for both Au super(+) states is significantly greater with CH sub(3)Cl than with CH sub(3)F. The observed two-body rate constant for depletion of Au super(+)( super(1)S) by CH sub(3)F represents less than 5% of the limiting rate constant predicted by the average dipole orientation model (ADO) at room temperature and 226 K, whereas CH sub(3)Cl reacts with Au super(+)( super(1)S) at the ADO limit at both room temperature and 218 K. Rate constants for depletion of Au super(+)( super(3)D) by CH sub(3)F and CH sub(3)Cl were measured at 226 and 218 K respectively, and indicate that Au super(+)( super(3)D) is consumed at approximately 2% of the ADO limit by CH sub(3)F and 69% of the ADO limit by CH sub(3)Cl. Product formation and overall efficiency for all four reactions are consistent with previous experimental results and available theoretical models.