Study on the oxygen quenching of photoexcited molecules by a thermal lens method at high pressure

本课题的主要目的是研制高压下热透镜信号测量仪。研制了常压热透镜测量装置，并通过对蒽类化合物的实验验证了该装置的性能。高压系统由高压泵、带四个光学窗口的高压容器和高压计组成，但高压样品池正在改进中，高压测量在新的未来是可行的，在常压测量中，发现非荧光碳基蒽除了系间交叉外，还发生了内转换。内转化率和系间交叉率的比值取决于溶剂。蒽类化合物的无辐射跃迁一直被认为是系间跃迁。这项研究中的新观察是研究非常快速内部转换的性质和机制的第一步。高压下的热透镜测量由于压力效应提供了介质效应的系统信息而有望成为一种有效的测量方法.在常压下的测量中，我们得到了氧猝灭受激态蒽化合物产生单氧的量子产率.对于大多数化合物，单线态氧不是由激发单线态的猝灭形成的，而是由激发三线态以大于80%的产率形成的。证实了9-氰基蒽的激发单线态形成单线态氧。利用热透镜方法研究了高压下单重态氧产生的介质依赖性。

The main object of this reseach is to make the instrument for measurement of thermal lens signal at high pressure. The apparatus for thermal lens measurement at normal pressure has been accomplished and its performance was confirmed by the experiment on the anthracene compounds. The high pressure system consisting of high pressure pump, high pressure vessel with four optical windows and high pressure gauge was made, but the sample cell for high pressure is now being improved and the measurement at high pressure will be feasible in the new future.In the measurement at normal pressure, the occurrence of internal conversion beside intersystem crossing was found for non-fluorescent cabonylanthracenes. The ratio between internal conversion and intersystem crossing depended on the solvent. It has so far been thought that the nonradiative transition for anthracene compounds is only intersystem crossing. The new observation in this research is the first step to investigate the nature and mechanism for the very fast internal conversion. The thermal lens measurement at high pressure is expected to become an effective method because the pressure effect give a systematic information on the medium effect.In the measurement at normal pressure, the quantum yield of prcduction of singletoxygen was obtained for the quenching of excited anthracene compounds by oxygen. It was suggested for most compunds that singlet oxygen was not formed from the quenching of the excied singlet state and it was formed at more yields than 80% from the excited triplet state. It was confirmed that singlet oxygen was formed from the excited singlet state of 9cyanoanthracene. The medium dependence of the singlet oxygen production is intended to be investigeted by the pressure effect based on the thermal lens method at high pressure.