An electron spin resonance study of single crystals of X-irradiated L-ascorbic acid at room temperature. Experimental results and semiempirical calculations

Abstract

X-irradiated crystals of L-ascorbic acid have been examined by e.s.r. spectroscopy in both the X and Q bands at room temperature. Three types of radicals have been observed. The forbidden transitions and ¹³C hyperfine splitting in its natural abundance have been detected. In order to determine the structure of all three radicals, the experimental results have been supported by semiempirical MNDO and INDO calcultions. Also, a method to calculate the dipolar hyperfine coupling tensor from a proton interacting with spin densities localised on two atoms has been used. The results are compared with the experimentally determined dipolar coupling tensors for distant hydroxy-group protons, interacting with spin densities localised on carbon and oxygen atoms.