Department of Chemistry, University of California, Berkeley, California 94720, USA and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Department of Chemical Engineering, University of Melbourne, Victoria 3010 Australia.
J Chem Phys. 2019 Nov 7;151(17):174303. doi: 10.1063/1.5121294.
Photofragment translational spectroscopy is used to investigate the unimolecular photodissociation of the indenyl radical (CH). CH radicals are generated by photodetachment of CH anions and are dissociated at 248 nm (5.00 eV) and 193 nm (6.42 eV). The following product channels are definitively observed at both wavelengths: CH + CH, CH + CH + CH, and CH + CH + CH. The three-body product channels are energetically inaccessible from single photon excitation at either dissociation wavelength. This observation, in combination with calculated dissociation rates and laser power studies, implies that all dissociation seen in this experiment occurs exclusively through multiphoton processes in which the initial CH radical absorbs two photons sequentially prior to dissociation to two or three fragments. The corresponding translational energy distributions for each product channel peak well below the maximum available energy for two photons and exhibit similar behavior regardless of dissociation wavelength. These results suggest that all products are formed by internal conversion to the ground electronic state, followed by dissociation.
光碎片平移谱学被用来研究茚基自由基（CH）的单分子光解。CH 自由基是通过 CH 阴离子的光脱附产生的，并在 248nm（5.00eV）和 193nm（6.42eV）处解离。在这两个波长下，明确观察到以下产物通道：CH + CH、CH + CH + CH 和 CH + CH + CH。在两个离解波长的单光子激发下，三个体产物通道在能量上是不可及的。这一观察结果，结合计算出的离解速率和激光功率研究，表明实验中观察到的所有离解都仅通过多光子过程发生，其中初始 CH 自由基在解离成两个或三个碎片之前，顺序吸收两个光子。每个产物通道的相应平移能分布都远远低于两个光子的最大可用能量，并表现出与离解波长无关的相似行为。这些结果表明，所有产物都是通过内部转化到基态电子态形成的，然后再进行离解。
