Huang Ting-Kang, Chen Bo-Jung, Lin King-Chuen, Lin Lin, Sun Bing-Jian, Chang A H H
Department of Chemistry, National Taiwan University, and Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan.
Department of Chemistry, National Dong Hwa University , Shoufeng, Hualien 974, Taiwan.
J Phys Chem A. 2017 Apr 20;121(15):2888-2895. doi: 10.1021/acs.jpca.6b12810. Epub 2017 Apr 5.
Cavity ring-down absorption spectroscopy (CRDS) is employed to investigate one-photon dissociation of (COCl) at 248 nm obtaining a primary Cl elimination channel. A ratio of vibrational population is estimated to be 1:(0.12 ± 0.03):(0.011 ± 0.003) for the v = 0, 1, and 2 levels. The quantum yield of Cl molecular channel is obtained to be 0.8 ± 0.4 initiated from the X̃ A ground state surface (COCl) via internal conversion. The obtained total quantum yield is attributed to both primary ((COCl) + hν → 2CO + Cl) and secondary reactions (dominated by Cl + COCl → Cl + CO). The former is estimated to share a yield of >0.14, while the latter contributes up to 0.66. The photodissociation pathway to the molecular products is calculated to proceed via a four-center transition state (TS) from which Cl is eliminated synchronously. Installation of the mirrors with reflectivity of 99.995% in the CRDS apparatus prolongs the ring-down time to 70 μs, thus allowing for the contribution from 17% up to 66% of the total Cl yield from secondary reaction depending on the reaction temperature. Despite uncertainty in determining the product yield, the primary Cl dissociation channel eliminated from (COCl) is observed for the first time.
采用腔衰荡吸收光谱法（CRDS）研究了248nm波长下（COCl）的单光子解离，得到了主要的Cl消除通道。对于v = 0、1和2能级，振动布居比估计为1:(0.12±0.03):(0.011±0.003)。通过内转换从X̃ A基态表面（COCl）引发的Cl分子通道的量子产率为0.8±0.4。得到的总量子产率归因于初级反应（(COCl) + hν → 2CO + Cl）和次级反应（主要由Cl + COCl → Cl + CO主导）。前者的产率估计大于0.14，而后者的贡献高达0.66。计算得出分子产物的光解离途径是通过一个四中心过渡态（TS）进行的，从中同步消除Cl。在CRDS装置中安装反射率为99.995%的镜子可将衰荡时间延长至70μs，因此根据反应温度，次级反应产生的Cl总产率的贡献从17%增加到66%。尽管在确定产物产率方面存在不确定性，但首次观察到了从（COCl）中消除的主要Cl解离通道。
