Molecular Relaxation by ESR Spectroscopy and Related Phenomena

在化学部实验物理化学计划的支持下，FREED将继续研究流体、表面和相关系统中的动态分子过程和自由基。将采用新的电子自旋共振(ESR)弛豫和结构技术，并将发展和扩展必要的理论框架。二维傅立叶变换(2D-FT)ESR、电子-电子双共振(2D-ELDOR)和远红外(FIR)ESR研究快慢运动区，将被应用于液体中的旋转分子动力学，提出了一个覆盖9-250 GHz的多频率方法。在适合液体研究的新光源和用于FIR-ESR的新的准光学方法的基础上，将在106 GHz发展脉冲ESR方法。研究的其他体系包括玻璃形成液体、微乳液等不均匀流体、表面受限的重定向动力学、简单和复杂液体中的平移扩散、液体中的双自由基和固体中的自由基团簇。核磁共振波谱已被成功地应用于从化学结构测定到医学诊断扫描的广泛应用。ESR光谱的相关技术发展缓慢，部分原因是必须使用的辐射频率和较短的弛豫时间(即人们可以测量被观察到的分子效应的时间)造成的障碍。这项研究计划将涉及电子自旋共振技术的发展和改进，这可能有助于使基于电子自旋共振的方法在化学、生物和材料科学中作为分析工具得到更普遍的使用。

In this project supported by the Experimental Physical Chemistry Program of the Chemistry Division, Freed will continue studies of dynamical molecular processes and free radicals in fluids, on surfaces, and in related systems. New electron spin resonance (ESR) relaxation and structural techniques will be employed, and the necessary theoretical frameworks will be developed and extended. Two-dimensional Fourier Transform (2D-FT) ESR, electron-electron double resonance (2D-ELDOR), and Far Infrared (FIR) ESR studies of fast and slow motional regimes will be developed and applied to rotational molecular dynamics in liquids, presenting a multi-frequency approach covering 9-250 GHz. Pulsed ESR methods will be developed at 106 GHz base on a new source appropriate for liquid studies and new quasi-optical methods for FIR-ESR. Other systems investigated will be glass-forming liquids, inhomogeneous fluids such as microemulsions, restricted reorientational dynamics on surfaces, translational diffusion in simple and complex liquids, biradicals in liquids, and radical clusters in solids. NMR spectroscopy has been successfully used in a wide range of applications, from chemical structure determination to medical diagnostic scanning. The related technique of ESR spectroscopy has been much slower to be developed in part because of obstacles caused by the frequencies of radiation which must be used and the shorter relaxation times, that is, the time during which one can measure the molecular effect being observed. This research program will involve the development and improvement of ESR techniques which may help to bring ESR-based methods into more common usage as analytical tools in chemistry, biology, and materials science.