29Si superhyperfine interactions of the E′ center: a potential probe of range-II order in silica glass

• Published in: Journal of non-crystalline solids Vol. 182; no. 1; pp. 119 - 134
• Main Authors: Griscom, D.L., Cook, M.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01-03-1995; Elsevier
• Subjects: Color centers and other defects; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron paramagnetic resonance and relaxation; Exact sciences and technology; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Physics; Gamma radiation; Tight binding approximation; ESR; Silicon oxides; Physical radiation effects; Glass; Experimental study; Superhyperfine interaction; Silica; Defects
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/0022-3093(94)00537-0

An electron spin resonance study has been carried out on E′
γ centers in γ-irradiated silica glasses of various
29Si enrichments, with the object of measuring superhyperfine splittings due to
29Si nuclei at the three closest silicon neighbors to the silicon of the unpaired spin. Experimental spectra obtained at X band (9.1 GHz) in the absorption mode and at Ka band (35.0 GHz) in the rapid-passage dispersion mode are compared with computer lineshape simulations based on a simple tight-binding model anchored to literature values of the so-called ‘weak’
29Si hyperfine splittings of the E′
1 center in α-quartz. Surprisingly few E′
γ sites are found in the glasses to exhibit such ‘weak’ splittings. To reconcile this result with the model assumption made by Mozzi and Warren and the supporting analyses of Galeener, it is suppose that dihedral angles in glassy silica might be relatively uniformly distributed and uncorrelated with the SiOSi angle distribution in the undamaged glass but that backward puckering relaxations (similar to that calculated by Rudra et al. for the E′
2 center in quartz) may be pervasive at E′
γ (oxygen vacancy) sites in glassy silica, causing dihedral angles in the range 100 ≲
α
1 ≲ 140° to be ‘read out’ in the present experiment as falling in the range 80 ≳
α
1 ≳ 40°