Electron Spin Resonance Study of Radical Pairs Trapped in Irradiated Single Crystals of Dimethylglyoxime at Liquid-Nitrogen Temperature

Abstract

The ESR spectra of x-irradiated single crystals of dimethylglyoxime have been measured at 77°K. An analysis of the spectra reveals that two paramagnetic species are produced by the irradiation. One is an iminoxy radical C(CH3)NOH–C(CH3)NO(M). The other, unstable at room temperature and containing two coupling nitrogen nuclei, is a radical pair with the mean distance between the two unpaired electrons of 5.6 Å. The absorption corresponding to the ΔM=2 transition of the radical pair has been observed in polycrystalline samples. The radical pair is tentatively identified to be the one consisting of adjacent radicals M···M along the crystallographic a axis.