ESR spectroscopy for analyzing the spatial distribution of free radicals in ammonium tartrate

Abstract

In the last few years the worldwide spread of radiation therapy with hadrons has stimulated the research on the effects produced by these particles on biological sys tems. This investigation on complex systems (such as cells) is aided by the study of the effects on simpler organic compounds in order to better model how the defects are produced by various types of ionizing radiations. Among the various experi mental techniques the contribution of electron spin resonance (ESR) spectroscopy is valuable because it does measure not only the total number of radiation-induced defects (and therefore the absorbed dose), but it can also provide useful information on the distribution of defects inside the matter and therefore on the linear energy transfer (LET) and quality of the radiations. In this work the applications of three experimental ESR methods for discriminating radiations with different quality on ammonium tartrate samples are reviewed. In particular, continuous wave ESR (cw ESR) spectroscopy allows to measure the ESR signal saturation with microwave power, whereas pulsed ESR spectroscopy permits to measure the microscopic local concentration by means of the analysis of the instantaneous diffusion and to measure the distance distribution through the Double Electron-Electron Resonance (DEER).