Chemical effects of heavy ion beams on organic materials

Effects of ion beam irradiation on alpha-alanine, adipic acid and polydimethylsiloxane were examined. Stable radicals were generated in the radiolysis of solids of alpha-alanine and adipic acid by gamma-ray, 220 MeV C ions, 350 MeV Ne ions and 175 MeV Ar ions. The G-value decreases in this order. The G-value for adipic acid decreases more than that for alpha-alanine. The decreases in the G-value are ascribed to high local dose in the ion tracks. Effective G-value of the radicals for gamma-irradiations decreases at high doses. The local dose in the ion tracks exceeds those doses, and the G-values for the ion irradiation are hence smaller than the G-value for gamma-irradiations. The difference in the dependence of the G-values for alpha-alanine and adipic acid on the ion beams is due to difference in the dose-yield relationship for radical formation. The high local dose in the ion tracks exceeds the gelation dose of some of polymers. Formation of gel strings of polydimethylsiloxanes generated in heavy ion tracks was observed by atomic force microscopy. (C) 2003 Elsevier Science B.V. All rights reserved.