Electron spin exchange relaxation of radicals in low magnetic field

Abstract

Spin relaxation of radicals caused by electron spin exchange (ESE) in solution at low and zero magnetic fields have been studied theoretically and experimentally using stable nitroxide radicals. It is shown that the probabilities of relaxation transitions in low and zero magnetic fields differ from the probabilities in high magnetic fields. The use of high-field expressions in low and zero magnetic fields is not correct. It is shown that ESE-induced relaxation leads to transfer of electron polarization to nuclear polarization. The theoretical predictions have been compared to experimental EPR spectra of nitroxide radicals in low magnetic fields.

Acknowledgements

This work was supported by Russian Foundation for Basic Research grants N 05-03-32370 and N 04-03-32604.