Lin Ming-Fu, Dyakov Yuri A, Tseng Chien-Ming, Mebel Alexander M, Lin Sheng Hsien, Lee Yuan T, Ni Chi-Kung
Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei, Taiwan.
J Chem Phys. 2005 Aug 1;123(5):054309. doi: 10.1063/1.1994849.
Photodissociation of pyridine, 2,6-d2-pyridine, and d5-pyridine at 193 and 248 nm was investigated separately using multimass ion imaging techniques. Six dissociation channels were observed at 193 nm, including C5NH5 --> C5NH4 + H (10%) and five ring opening dissociation channels, C5NH5 --> C4H4 + HCN, C5NH5 --> C3H3 + C2NH2, C5NH5 --> C2H4 +C3NH, C5NH5 --> C4NH2 + CH3 (14%), and C5NH5 --> C2H2 + C3NH3. Extensive H and D atom exchanges of 2,6-d2-pyridine prior to dissociation were observed. Photofragment translational energy distributions and dissociation rates indicate that dissociation occurs in the ground electronic state after internal conversion. The dissociation rate of pyridine excited by 248-nm photons was too slow to be measured, and the upper limit of the dissociation rate was estimated to be 2x10(3) s(-1). Comparisons with potential energies obtained from ab initio calculations and dissociation rates obtained from the Rice-Ramsperger-Kassel-Marcus theory have been made.
分别使用多质量离子成像技术研究了吡啶、2,6 -二氘代吡啶和五氘代吡啶在193和248 nm处的光解离。在193 nm处观察到六个解离通道，包括C5NH5 --> C5NH4 + H（10%）和五个开环解离通道，C5NH5 --> C4H4 + HCN、C5NH5 --> C3H3 + C2NH2、C5NH5 --> C2H4 + C3NH、C5NH5 --> C4NH2 + CH3（14%）以及C5NH5 --> C2H2 + C3NH3。观察到2,6 -二氘代吡啶在解离前有广泛的H和D原子交换。光碎片平动能量分布和解离速率表明，解离在内部转换后发生在基电子态。248 nm光子激发的吡啶解离速率太慢无法测量，解离速率的上限估计为2×10³ s⁻¹。已将其与从头算计算得到的势能以及从赖斯 - 拉姆齐 - 卡斯尔 - 马库斯理论得到的解离速率进行了比较。
