ESR Imaging and Its Applications

Abstract

An electron spin resonance (ESR) image is a representation of the spatial distribution of the ESR signal intensity or other parameter in a heterogeneous sample as well as NMR imaging. ESR is a well-established method for the study of many properties of matter, and is currently applied in a variety of fields, even archaeology. Beyond the recent development of various ESR techniques, much wider applications of ESR imaging are demanded and can be expected. In the field of solid-state physics, the possibility exists of measuring the distribution and diffusion of paramagnetic donor and acceptor centers, and paramagnetic centers adsorbed on interfaces. The investigation of the reaction and the diffusion of organic free radicals in the amorphous solid state, especially in high polymers and catalysts, means a further application in chemistry. Observation of the distribution of free radicals after mixing flowing reagents in a cavity is of interest for investigations on the dynamics of chemical reactions. This concept leads to other fields of application including the diffusion of spin probes in liquid crystals and the dynamics of development or novel detection systems for chromatography. In biology and medicine the distribution of natural paramagnetic centers in tissue slices, the distribution pattern of probe molecules (spin probe) in membranes, and the diffusion profiles of spin-labeled drug in tissues are all subjects of extreme interest. In archaeology the possibility of invasive date determination or archaeological analysis exists. Thus, if ESR imaging i s put to practical use, more valuable functions will be added to ESR spectroscopy.