Electron-electron double resonance study of trapped electrons in γ-irradiated 2-methyltetrahydrofuran glass: Magnetic energy transfer between two different spin systems

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Abstract
Electron-electron double resonance (ELDOR) of trapped electrons and radicals in γ-irradiated 2-methyltetrahydrofuran (MTHF) glass at 77°K was investigated. Magnetic energy pumped into the radical spin system is transferred to the trapped electron spin system to partially saturate it. The cross saturation mechanism is consistent with dipolar cross relaxation in which a radical spin flips down and an electron spin flips up. Analysis of the rate of spin relaxation shows that the reciprocal ELDOR reduction is linear with pumping microwave power with an intercept which gives the ratio of the cross-relaxation time to the electron spin-lattice relaxation time. The experimental data are found to fit this relationship. This ratio of relaxation times is of the order of 0.5 while the relaxation times themselves are in the 10−4-sec range. The observation of cross relaxation in this system supports the concept that the trapped electron and radical are spatially correlated in γ-irradiated MTHF.