Transmittance in irradiated poly(methyl methacrylate) at elevated temperatures

The transient transmittance of gamma-ray irradiated poly(methyl methacrylat e) at elevated temperatures is investigated. The transmittance in the ultra violet and visible range decreases with an increase of radiation dose. We p ropose that the color center is responsible for the reduction of transmitta nce in the irradiated specimen. Then the concentration of the color center decreases with increasing annealing time at elevated temperatures. The tran smittance data at 407 nm are in excellent agreement with the theoretical mo del in which the color center is annihilated by a second order kinetic proc ess. The rate constant follows the Arrhenius equation. The activation energ y in the range of 44.27-51.52 kJ/mol decreases with increased dose. (C) 200 0 American Institute of Physics. [S0021-8979(00)06622-6].