Spectroscopy and photochemistry of acetylene adsorbed on NaCl(100)
Spectroscopy and photochemistry of acetylene adsorbed on NaCl(100)
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乙炔吸附在 NaCl(100) 上的光谱和光化学
DOI：
10.1116/1.578413
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
G. Ewing
中科院分区：
文献类型：
--
作者：
S. Dunn;G. Ewing
用偏振红外吸收光谱测定了乙炔物理吸附在氯化钠(100)上的分子倾斜度和取向。用类似于乙炔低温晶相的有序结构定性地解释了这些光谱。我们还发现了该系统存在高温、无序晶格气相的证据。在184.9 nm光照射下，晶格气体发生氢交换反应，而结构相是无反应的。与气相光解不同，气相光解产生聚合物、分子氢和一系列小碳氢化合物，在表面相反应中没有观察到乙炔同位素异构体以外的其他产物。反应速率与温度呈指数关系，并被解释为表面扩散受限。我们认为这种光化学氢交换是通过自由基链式反应进行的。
Polarized infrared absorption spectroscopy is used to determine molecular tilt and orientation of acetylene physisorbed to NaCl(100). The spectra are qualitatively explained by an ordered structure similar to the low‐temperature crystalline phase of acetylene. We also find evidence for a high‐temperature, disordered lattice‐gas phase of this system. Upon exposure to 184.9 nm light the lattice gas undergoes a hydrogen exchange reaction, while the structured phase is unreactive. In contrast to gas‐phase photolysis, which yields a polymer, molecular hydrogen, and a collection of small hydrocarbons, no products other than acetylene isotopomers are observed in the surface‐phase reaction. The rate of the reaction shows an exponential temperature dependence and is interpreted as being surface diffusion limited. We propose that this photochemical hydrogen exchange occurs by a radical chain reaction.