State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Liaoning, Dalian 116023, China.
Phys Chem Chem Phys. 2011 May 14;13(18):8531-6. doi: 10.1039/c1cp00032b. Epub 2011 Mar 30.
The SH + CH(3) product channel for the photodissociation of CH(3)SH at 204 nm was investigated using the sliced velocity map ion imaging technique with the detection of CH(3) products using state selective (2+1) resonance enhanced multiphoton ionization (REMPI). Images were measured for CH(3) formed in the ground and excited vibrational states (v(2) = 0, 1, and 2) of the umbrella mode from which the correlated SH vibrational state distributions were determined. The vibrational distribution of the SH fragment in the SH + CH(3) channel at 204 nm is clearly inverted and peaks at v = 1. The highly negative anisotropy parameter of the CH(3) (v(2) = 0, 1, and 2) products is indicative of a fast dissociation process for C-S bond cleavage. Two kinds of slower CH(3) products were also observed (one of which was partly vibrationally resolved) that are assigned to a two-step photodissociation processes, in which the first step is the production of the CH(3)S (X(2)E) radical via cleavage of the S-H bond in CH(3)SH, followed by probe laser photodissociation of nascent CH(3)S radicals yielding CH(3)(X(2)A(1), v(2) = 0-2) + S((3)P(j)/(1)D) products.
在 204nm 处，利用切片速度图离子成像技术研究了 CH3SH 的光解的 SH+CH3 产物通道，同时使用状态选择性（2+1）共振增强多光子电离（REMPI）检测 CH3 产物。测量了 CH3 在伞式模式的基态和激发振动态（v2=0、1 和 2）中形成的图像，从中确定了相关的 SH 振动态分布。在 204nm 处，SH+CH3 通道中 SH 碎片的振动分布明显反转，峰值在 v=1 处。CH3（v2=0、1 和 2）产物的高度负各向异性参数表明 C-S 键断裂的快速解离过程。还观察到两种较慢的 CH3 产物（其中一种部分在振动上得到分辨），它们被分配到两步光解过程中，其中第一步是通过 CH3SH 中的 S-H 键断裂产生 CH3S（X2E）自由基，然后通过初生 CH3S 自由基的探针激光光解生成 CH3（X2A1，v2=0-2）+S（（3）P（j）/（1）D）产物。
