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Density fluctuation of fluids and dynamics of photo-dissociation reactions

流体的密度波动和光解反应动力学

基本信息

批准号：
07640673
负责人：
KIMURA Yoshifumi
金额：
$ 1.47万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07640673/
关键词：
Supercritical Fluid Charge Transfer Complex Electron Transfer Rate Radical Pair Disulfide Complex Photolysis Quantum Yield ラジカル対

项目摘要

In order to reveal the dynamics of the molecular pair created by the photo-excitation in supercritical fluids with the large density fluctuation, we have studied two reaction systems ; the charge transfer complex which creates the charge-separated excited state upon photo-excitation, and disulfide compounds which creates the radical pair upon photo-excitation. We have chosen the charge transfer complex of hexamethylbenzene and tetracyanoethylene as the former system, and measured the relaxation process from the excited state in several fluids (ethane, carbon dioxide, trifluoromethane, and nitrous oxide) by the pico-second transient absorption method. According to the results, the electron transfer rate from the excited state increases with increasing the solvent polarity and the solvent density. The relative change of the electron transfer rate in various conditions has been well reproduced by the theoretical calculation using the reaction free energy and the solvent reorganization energy estimated from the absorption spectrum. The electron transfer rate showed a significant isotope effect, which could not be reproduced by the theoretical calculation.We have applied the transient grating method to the measurement of the photolysis quantum yield, and have succeeded in determining the photolysis quantum yield of diphenyl disulfide in supercritical fluids. The density dependence of the photolysis quantum yield and the non-geminate recombination rate could not be explained by the model used for the recombination process of iodine. Our results suggests the possibility of the primary geminate recombination just after the photo-excitation. We have also succeeded in measuring the absorption spectrum in pico-second order time resolution using the high pressure flow system constructed in this study. Now we are analyzing the rise process of the absorption of the radical just after the creation, in several fluids.

为了揭示具有大密度波动的超临界流体中光激发产生的分子对的动力学，我们研究了两个反应体系；电荷转移络合物在光激发时产生电荷分离的激发态，二硫化物在光激发时产生自由基对。我们选择六甲基苯和四氰乙烯的电荷转移络合物作为前体系，并通过皮秒瞬态吸收法测量了几种流体（乙烷、二氧化碳、三氟甲烷和一氧化二氮）中从激发态开始的弛豫过程。结果表明，激发态的电子转移速率随着溶剂极性和溶剂密度的增加而增加。使用反应自由能和从吸收光谱估计的溶剂重组能的理论计算很好地再现了各种条件下电子转移速率的相对变化。电子转移速率表现出明显的同位素效应，理论计算无法重现。我们将瞬态光栅方法应用于光解量子产率的测量，并成功测定了超临界流体中二苯基二硫醚的光解量子产率。光解量子产率和非成对复合率的密度依赖性无法通过用于碘复合过程的模型来解释。我们的结果表明光激发后可能发生初级双子重组。我们还使用本研究中构建的高压流系统成功地测量了皮秒级时间分辨率的吸收光谱。现在我们正在分析几种液体中自由基产生后吸收的上升过程。