Rates of rotational diffusion and heisenberg spin exchange as obtained from CW ESR and ESR tomographic experiments on model systems and human skin

摘要

The purpose of the present paper is to describe possibilities and limitations for the determination of the rates of rotational diffusion and Heisenberg spin exchange, obtained from continuous-wave electron spin resonance (cw ESR) and ESR tomographic experiments. Model systems including nitroxides as paramagnetic reporter molecules have been examined in order to verify data, which have been obtained from cw ESR and ESR tomography. This has been done with particular emphasis on checking the influence of concentration, temperature, and viscosity on the spectral-spatial properties. These findings have been applied to the evaluation of penetration and permeation studies on human skin. The extracted full spectral information from ESR tomography allows the determination of the above mentioned dynamic parameters for model systems of definite geometry and for samples of human skin. It has been found that the signal-to-noise ratio is critical for all discussed applications.