Electron spin resonance and proton ENDOR studies in potassium hydrogen oxalate single crystals

Abstract

Radicals trapped in a γ-irradiated single crystal of potassium hydrogen oxalate have been investigated using ESR and ENDOR techniques. The CO^–₂ radical produced exhibited hyperfine interaction with nearby protons, and detailed ENDOR study revealed that one of these protons was partially transferred onto the radical site along the hydrogen bridge. Theoretical interpretation of the dipolar couplings indicate that the shift form the crystallographic position of this proton is small. A second species was observed and tentatively assigned to a protonated anion radical. These findings are discussed in relation to the anomalous couplings observed in sodium hydrogen oxalate monohydrate.