Savee John D, Borkar Sampada, Welz Oliver, Sztáray Bálint, Taatjes Craig A, Osborn David L
†Combustion Research Facility, Sandia National Laboratories, Mail Stop 9055, Livermore, California 94551-0969, United States.
‡Department of Chemistry, University of the Pacific, Stockton, California 95211, United States.
J Phys Chem A. 2015 Jul 16;119(28):7388-403. doi: 10.1021/acs.jpca.5b00491. Epub 2015 May 18.
The reaction of O((3)P) + propyne (C3H4) was investigated at 298 K and 4 Torr using time-resolved multiplexed photoionization mass spectrometry and a synchrotron-generated tunable vacuum ultraviolet light source. The time-resolved mass spectra of the observed products suggest five major channels under our conditions: C2H3 + HCO, CH3 + HCCO, H + CH3CCO, C2H4 + CO, and C2H2 + H2 + CO. The relative branching ratios for these channels were found to be 1.00, (0.35 ± 0.11), (0.18 ± 0.10), (0.73 ± 0.27), and (1.31 ± 0.62). In addition, we observed signals consistent with minor production of C3H3 + OH and H2 + CH2CCO, although we cannot conclusively assign them as direct product channels from O((3)P) + propyne. The direct abstraction mechanism plays only a minor role (≤1%), and we estimate that O((3)P) addition to the central carbon of propyne accounts for 10% of products, with addition to the terminal carbon accounting for the remaining 89%. The isotopologues observed in experiments using d1-propyne (CH3CCD) and analysis of product branching in light of previously computed stationary points on the singlet and triplet potential energy surfaces (PESs) relevant to O((3)P) + propyne suggest that, under our conditions, (84 ± 14)% of the observed product channels from O((3)P) + propyne result from intersystem crossing from the initial triplet PES to the lower-lying singlet PES.
利用时间分辨多路光电离质谱和同步加速器产生的可调谐真空紫外光源，在298 K和4托的条件下研究了O((3)P)与丙炔（C3H4）的反应。观测产物的时间分辨质谱表明，在我们的条件下有五个主要通道：C2H3 + HCO、CH3 + HCCO、H + CH3CCO、C2H4 + CO和C2H2 + H2 + CO。发现这些通道的相对分支比分别为1.00、(0.35 ± 0.11)、(0.18 ± 0.10)、(0.73 ± 0.27)和(1.31 ± 0.62)。此外，我们观测到了与C3H3 + OH和H2 + CH2CCO少量生成相一致的信号，尽管我们不能确定地将它们归为O((3)P) + 丙炔的直接产物通道。直接夺取机制仅起次要作用（≤1%），我们估计O((3)P)加到丙炔中心碳上的产物占10%，加到末端碳上的产物占其余的89%。在使用d1-丙炔（CH3CCD）的实验中观测到的同位素异构体，以及根据先前计算的与O((3)P) + 丙炔相关的单重态和三重态势能面（PESs）上的驻点对产物分支进行的分析表明，在我们的条件下，O((3)P) + 丙炔观测到的产物通道中(84 ± 14)%是由初始三重态PES到较低单重态PES的系间窜越产生的。
