ESR and proton ENDOR studies in single crystals of ammonium hydrogen 1-malate

The techniques of ESR and ENDOR have been used to study the radicals trapped in a γ-irradiated single crystal of ammonium hydrogen 1-malate. A radical of the type HOOC-CH2-ĊOH-COO was observed and analysed. The ENDOR experimental tensors showed considerable deviations from those expected from the undamaged crystal structure. An idealized model is proposed for explaining the observed discrepancies. At atomic rearrangement involving re-hybridization together with rotation of a methylene group appear to qualitatively account for the discrepancy. 13C satellites were observed and analysed.