Development of a new spectroscopy based on several transient lens effects and its application to chemical reactions

光化学反应中的反应体积变化和焓变是表征反应的重要量。然而，缺乏合适的方法来检测这些量具有足够高的灵敏度和高的时间分辨率，阻碍了我们对许多化学反应的详细了解。在这项研究中，我们已经开发出了新的技术，用于测量这些量的高灵敏度和高时间分辨率，使用所谓的“热透镜”设置。我们已经发现了光激发后透镜信号的各种来源，如布居透镜、温度透镜、克尔透镜和体积透镜。利用这些元件，在恒温、恒压的条件下，成功地测量了溶剂中化学反应和物理过程的反应体积、焓变、偏摩尔体积和热能。因此，我们提出了一个新的名称“瞬态透镜方法”的这些技术。此外，我们还发现了溶液中有机分子光激发后观察到的瞬态光栅信号的各种来源，如温度光栅，团簇光栅和体积光栅。利用光栅技术研究了化学反应中瞬态自由基的平移扩散过程。自由基的扩散常数被发现是非常小的相比，具有类似的大小和形状的非自由基分子。通过温度依赖性和分子尺寸依赖性详细研究了这一反常扩散过程。本研究将揭示自由基-溶剂分子间相互作用的一个有趣的领域。

Reaction volume changes and enthalpy changes in a photochemical reaction are very important quantities to characterize the reaction. However, a lack of suitable method for detecting these quantities with a sufficiently high sensitivity and high time resolution prohibits our detailed understanding of many chemical reactions. In this study, we have developed new techniques for measuring these quantities with high sensitivity and high time resolution using the so-called 'thermal lens' setup. We have discovered various origins of the lens signals after the photoexcitation, such as the population lens, temperature lens, Kerr lens, and volume lens. By using these components, the reaction volume, enthalpy change, partial molar volume and heat energy form chemical reactions and photophysical processes are successfully measured under a constant temperature, and a constant pressure in a solvent. Therefore we proposed a new name "transient lens method" for these techniques. Furthermore we have discovered various origins for the transient grating signals observed after photoexcitation of organic molecules in solutions, such as temperature grating, cluster grating, and volume grating. By using the grating technique, the translational diffusion process of transient radicals appeared in chemical reactions is investigated. The diffusion constants of the radicals are found to be very small compared with the non-radical molecules with similar sizes and shapes. This anomalous diffusion process is studied in detail by the temperature dependence and molecular size dependence. This study will reveal an interesting field of radicalsolvent intermolecular interaction.