Development of Local Relaxation Spectroscopy using 2D Correlation Methods

点击翻译按钮获取中文摘要

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