Radiogenic free radicals in apatite: the influence of fluoride and hydroxide

Fluor-hydroxyapatites of varying fluoride and hydroxide contents were irradiated by soft x-rays at -188 degrees C and examined by means of electron spin resonance spectroscopy. Variation in fluoride-hydroxide contents affected radical yield and resulted in the observation of two kinds of oxygen anion resonances: a doublet due to hydrogen hyperfine splitting and a singlet. At higher temperatures a spin transfer process became operative which enhanced the oxygen anion radical population. Increasing fluoride content was paralleled by decreasing g-values for the oxygen anion resonances, possibly attributable to increased delocalization of the unpaired spin.