Experimental study of the reaction of molecules whose vibrational distribution is perturbed.

研究局域振动激发态分子与普通分子的不同行为在化学动力学领域中具有重要意义。理论上，这是讨论的基础上的IRC和其他之间的振动模式的耦合。另一方面，由于制备方法的困难，实验研究的报道较少。本课题尝试将冲击加热法与CO_2红外激光照射相结合来观察反应行为。用这种方法发现，丙烯腈在激光辐照后的冲击加热区发生了分解。由于激光功率小于10 mJ，激光照射只是扰动振动态的热分解，产生局域振动激发分子的另一种方法是相对较大分子的热分解。如果乙基乙烯基醚单分子分解，则产生乙醛和乙烯。该反应的过渡态具有六中心结构，表明产物醛的甲基以转动或H-C-H弯曲模式被强烈激发。因此，可以预期，在该monnor中产生的乙醛表现出不寻常的动力学。事实上，我们发现这种醛的分解速率常数比通常值大得多，因此，我们确定了振动的局部激发对单分子分解速率的影响是敏感的。

It is very important in the field of chemical kinetics to investigate that local-vibration-excited molecules behave different mannor from the usual molecules. Theortically, this is discussed on the basis of the coupling of the vibrational modes between the IRC and others. On the other hand, there are few report on the experimental study because of the difficulty of the obserbation. In this project, we tried to observe the reaction behavior by connecting the shock heating method and CO_2 infra-red laser shot. With this method it was found that acrylonitrile was decomposed after laser shot in the shock heated region. Since the laser power was less than 10mJ, laser shot merely perturbed the thermal disrtribution of the vibrational states.The other method to produce local-vibration-excited molecules was the thermal decompositon of relatively large molecules. If ethyl vinyl ether is decomposed unimolecularly, acetaldehyde and ethylene are produced. The transition state of this reaction have a 6-centered structure and this structure suggests that the methyl group of the product aldehyde is strongly excited in the rotation or H-C-H bending mode. Therefore, it is expected that the acetaldehyde produced in this monnor behaves unusual kinetics. In fact, we found that this aldehyde decomposed with very large rate constants compared with the usual value.Thus, we ascertained that the local excitation of vibrations affected sensitively the unimolecular decomposition rate.