Electron Spin-Lattice Relaxation at Defect Sites;E′Centers in Synthetic Quartz at 3 Kilo-Oersteds

Enhanced Signal Intensities Obtained by Out-of-Phase Rapid-Passage EPR for Samples with Long Electron Spin Relaxation Times

“…The room temperature signal was selected as the reference because the resulting value reflects the potential advantage in signal intensity that could be achieved by recording spectra at lower temperatures. T 1 for the E signal increased with decreasing temperature (22). For the samples studied here, about 25% larger B 1 was required to achieve the maximum out-of-phase signal at 100 K than at room temperature because of the increase in T 1 .…”

“…It is assigned as an oxygen vacancy site at which the unpaired electron occupies a dangling sp 3 hybrid orbital of a silicon that is bonded to three oxygens. Several groups have characterized E centers in amorphous and crystalline SiO 2 (12,13,(21)(22)(23)(24)(25)(26)(27)(28).…”

Review of some experiments in the 50 year saga of the E′ center and suggestions for future research

“…In the case of a spin state with S = 1/2 there is only one excited state. Castle et al [16] used a method called inversion-recovery time at a range of temperatures, 1.24-250 K to measure the temperature dependence of the recovery time of the E 0 1 , E 0 2 , and a center they labeled C, in c-ray irradiated single crystals of the alpha quartz form (hereafter alpha quartz) of SiO 2 and Castle and Feldman [24] measured the temperature dependence of the spin-lattice relaxation time of the E 0 c center in a Type III silica. They [25] also repeated the measurements on the E 0 1 center in the samples used in the first measurements of the temperature dependence of the spin relaxation time.…”

“…The magnitude of f ij can be inferred experimentally from the absorption coefficient, a(hx) and an independent measurement of N. Knowing a and N, Smakula's equation can be used for dielectrics such as silica [14,16]. A value 61 is expected for single electron states, therefore an oscillator strength >1 indicates that more than one optical active bands must be present that absorbs at or close to the same energy.…”

Coherent spin dynamics in a gadolinium-dopedCaWO4crystal

“…The index 4 n  differed slightly from 3 n  and 3.6 that had been obtained previously [25]. According to the existing models of the spin-lattice relaxation of an S-state ion [31] and of the paramagnetic center situated at the defect site [32], 3 were successfully simulated by the following expression [33,34]:…”