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The electron spin relaxation time, T1, of the E′ defect in γ-irradiated vitreous silica, was measured by time-domain EPR and found to be approximately independent of microwave frequency between 1 and 9 GHz and to increase by about 50% at 19.4 GHz. Preliminary results indicate a further increase in T1 at 95 GHz. At each microwave frequency, T1 varies monotonically with position in the EPR line. T1 is longer near the parallel axis and shorter in the perpendicular plane of the g-axis system. T1 is interpreted in terms of coupling to local vibrational modes of the defect center. The electron-spin-echo phase-memory time, Tm, extrapolated to small B1, is independent of microwave frequency. It is equal to the electron spin T2 determined by electron-electron dipole interaction. |
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