Isothermal Decay of Trapped Electron in Irradiated 2-Methyltetrahydrofuran Glass

概要

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The isothermal decay of the electron trapped in gamma-irradiated 2-methyltetrahydrofuran glass was studied by electron spin resonance measurements at 92–95 K. Shape of the decay curves was found to be independent not only of radiation dose but also of temperature if they were plotted on the time scale in unit of half-life at each temperature studied. Although the decay follows neither a first order nor a second order reaction, the activation energy is able to be determined uniquely to be 0.8 eV. These results indicate that the mobilization of trapped electron is caused by repeated sequences of detrap-retrap due to thermal distortion or destruction of traps and that the evolution of decay is determined by the initial distribution of the electron-cation separation. On the basis of Nernst-Einstein assumption, the normalized distribution of the separation distance is numerically obtained and found to be close to a Gaussian function, though the absolute value of distance is unable to be determined because of the lack of knowledge of diffusion coefficient for the migration of electron in the glass. The effect of partial photobleaching of the trapped electron on the isothermal decay for the rest of electron was also studied and found to be the same as that of partial thermal bleaching.
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