Development of Local Relaxation Spectroscopy using 2D Correlation Methods

凝聚态物质对外场扰动的动态响应直接告诉我们系统自发涨落模的动力学。为了研究材料的动态特性，介电和粘弹性等弛豫谱得到了广泛的应用。这种光谱学是测量热力学共轭变量对外场的响应，作为其频率的函数。这种宏观弛豫光谱是研究材料动力学的一种非常有效的手段，但它不能在分子水平上为我们提供微观信息。为了提取关于驰豫机制的分子水平信息，我们一直需要一个连接微观和宏观世界的物理模型。另一方面，红外、拉曼和核磁共振光谱给我们提供了直接的分子水平信息，如分子的成键状态和局部构象。…然而，到目前为止，这些光谱技术还没有被应用于动态弛豫现象，它们的应用仅限于对静态结构的研究，这种类型的光谱对局部化学键的构型和环境非常敏感，因为它利用了局部结构单元的共振现象。因此，基于上述光谱技术的动态弛豫谱应该是直接给出分子级结构单元驰豫行为信息的终极弛豫谱。通过研究各个结构单元对外场扰动的动态响应，可以在分子水平上阐明弛豫机理。基于这一思想，我们在阶跃扫描型干涉仪的基础上发展了一种新型的2D-FTIR弛豫光谱。2D-FTIR的基本原理已由Noda进一步发展，具有研究二维相关红外光谱的频率依赖性的能力。我们成功地测量了线性区域中的弛豫现象，它是外场频率的函数。时间分辨红外光谱是由许多研究人员发展起来的，然而，其应用到目前为止还局限于铁电材料的非线性开关现象，这主要是因为S/N比相当低。我们相信，我们的3D-FTIR光谱首次为我们提供了一个真正的弛豫光谱，它具有线性响应区域中的分子水平信息。较少

The dynamic response of a condensed matter to the perturbation due to the external fields directly tells us on the dynamics of the spontaneous fluctuation modes of the system. To study the dynamic properties of a material, the relaxational spectroscopy such as dielectric and viscoelastic spectroscopy has been widely used so far. Such a spectroscopy is to measure the response of the thermodynamically conjugated variable to the external field as a function of its frequency. This type of macroscopic relaxational spectroscopy is a very powerful mean to study the dynamics of a material, however, it does not provide us with microscopic information at the molecular level. To extract the molecular-level information on the relaxation mechanism, we have always needed a physical model which connects the microscopic and macroscopic world.Infrared, Raman, and NMR spectroscopy, on the other hand, gives us direct molecular-level information such as bonding states and local conformation of molecules. … More However, these spectroscopic techniques have not so far been applied to the dynamic relaxational phenomena, and their application has been limited to the study of the static structure.This type of spectroscopy is very sensitive to the local configuration and environment of chemical bonds, since it uses the resonance phenomena of local structural units. Thus, the dynamic relaxational spectroscopy based on the above spectroscopic techniques should be the ultimate relaxational spectroscopy which directly gives the information on the relaxational behavior of the molecular-level structural units. By studying the dynamic response of each structural units to the perturbation due to an external field, we can elucidate the relaxational mechanism on the molecular level.Along this idea, we have developed a new type of 2D-FTIR relaxational spectroscopy on the basis of the step-scan-type interferometer. 2D-FTIR whose basic principale has been developed by Noda has further been advanced to have ability of studying the frequency dependence of a 2D correlation IR spectrum. The relaxational Phenomena in a linear regime have been successfully measured as a function of the frequency of the external field. The time-resolved infrared spectroscopy was developed by many researchers, however, its application has up to now been limited to the nonlinear switching phenomena of ferroelectric materials, primarily because of the rather poor S/N ratio. We believe that our 3D-FTIR spectroscopy is the first to provide us with a true relaxational spectroscopy withe the molecular-level information in a linear-response-regime. Less