Radiation chemistry in alanine irradiated with γ-rays and ion beams

In order to extend the application of alanine dosimetry, the behavior of free radicals in solid α-alanine irradiated with γ-rays with ions beams was studied by electron spin resonance. Stable neutral radicals are produced through the decomposition of originally generated ion radicals in alanine irradiated at 300 K, while at 77 K the ion radicals are stable, and also do not decompose. The rate of the combination reaction of the neutral radicals and of the iron radicals was studied by measuring the saturation behavior of the radical concentration in γ-radiolysis at 300 and at 77 K. The yield of the neutral radicals was compared between 0.5, 1, 2 and 3 MeV H+, 0.5, 1,and 3 MeV He+, 175 MeV Ar8+ and 460 MeV Ar13+ ion irradiations. Dependence of the radical yield on the radiation quality is understood more in terms of the rate of the combination reaction between the ion radicals that with that between the neutral radicals, and has to do with high local dose within the ion tracks.