Paramagnetic Relaxation Study of Spatial Distribution of Trapped Electrons in Gamma-Irradiated Organic Glasses

Abstract

Paramagnetic relaxation characteristics of trapped electrons in γ-irradiated glassy 3-methylpentane (3-MP) at 71°K, and triethylamine (TEA) and methyltetrahydrofuran (MTHF) at 77°K were studied by power saturation techniques. For MTHF and TEA the characteristic relaxation time, (T1T2)1/2, is constant with radiation dose at low doses and decreases at higher doses. For 3-MP the relaxation time decreases even at low dose. Together with data on the total spin concentration the results are interpreted in terms of a ``spur'' model in which the radiation-produced trapped electrons and radicals are trapped in clusters at low dose and constitute a nonuniform spatial distribution. According to this model the spur radius is 〉130 Å in 3 MP, 101 Å in TEA, and 63 Å in MTHF. These radii compare with 58 Å for trapped electrons in glassy methanol and 41 Å in glassy alkaline ice (10M NAOH). For all of these matrices the radius within which the electrons are trapped appears to increase with decreasing polarity of the matrix, and consequently radiation-produced electrons appear to travel farther before being trapped in less polar matrices.