Search

Polycrystalline hexagonal ice containing thymine was γ-irradiated at 77 K, and X-band electron paramagnetic resonance spectra of the resulting radicals were recorded at this temperature immediately after irradiation, and after thermal annealing of the samples at temperatures up to 250 K. The examined frozen samples were obtained from hyperquenched glassy aqueous solution containing 0.005 M of thymine, by using two different procedures: (i) crystallization of the glass by heating up to 250 K, and (ii) warming the glass up to room temperature to melt it, and subsequent cooling of the solution in liquid N2. Thymine-derived radicals were detectable only in the samples obtained by crystallization of the glass. We conclude that the extent of solute segregation is less for the frozen aqueous solution made by route (i) than by route (ii). Therefore, the solute is more hydrated in the frozen sample made by route (i) and the primary products of water radiolysis can react with the solute. The present results are compared with those reported for the thymine/hyperquenched glassy water system (Bednarek et al. , J. Phys. Chem. B 103 , 6824 (1999)). [ABSTRACT FROM AUTHOR]