Rösch Daniel, Xu Yifei, Guo Hua, Hu Xixi, Osborn David L
Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, United States.
Institute of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China.
J Phys Chem Lett. 2023 Mar 30;14(12):3084-3091. doi: 10.1021/acs.jpclett.3c00077. Epub 2023 Mar 23.
It is well-documented that photodissociation of SO at λ = 193 nm produces O(P) + SO X(Σ). We provide experimental evidence of a new product channel from one-photon absorption producing S(P) + O X(Σ) in 2-4% yield. We probe the reactant and all products with time-resolved photoelectron photoion coincidence spectroscopy. High-level ab initio calculations suggest that the new product channel can only occur on the ground-state potential energy surface through internal conversion from the excited state, followed by isomerization to a transient SOO intermediate. Classical trajectories on the ground-state potential energy surface with random initial conditions qualitatively reproduce the experimental yields. This unexpected photodissociation pathway may help reconcile discrepancies in sulfur mass-independent fractionation mechanisms in Earth's geologic history, which shape our understanding of the Archean atmosphere and the Great Oxygenation Event in Earth's evolution.
有充分文献记载，在λ = 193 nm处SO的光解离会产生O(P) + SO X(Σ)。我们提供了实验证据，证明单光子吸收产生S(P) + O X(Σ)的新产物通道，产率为2 - 4%。我们用时间分辨光电子光离子符合光谱法探测反应物和所有产物。高水平的从头算计算表明，新的产物通道只能通过从激发态的内转换，然后异构化为瞬态SOO中间体，在基态势能面上发生。在具有随机初始条件的基态势能面上的经典轨迹定性地再现了实验产率。这种意想不到的光解离途径可能有助于调和地球地质历史中硫的质量无关分馏机制的差异，这些差异塑造了我们对太古宙大气和地球演化中的大氧化事件的理解。
