Kinetics of radical decay in crystalline amino acids

The disappearance of free radicals in irradiated polycrystalline and single-crystal amino acids has been studied by esr at 23°C. The decay appears to be second order in radical concentration and the rate is consistent with a vacancy-controlled bulk diffusion process. The acids studied include DL and L-leucine in polycrystalline and single crystalline forms, as well as DL-valine in polycrystalline form. L-Valine and L-isoleucine were studied in both poly and single crystalline form. The second order decay constants ranged from $3.9\times 10^{-21}$ to $2.2\times 10^{-14}$ grams $\text{spins}^{-1} \text{minutes}^{-1}$.