PURE NUCLEAR-QUADRUPOLE RESONANCE SPECTROSCOPY STUDIES OF THE STRUCTURE OF GLASSES

Pure nuclear quadrupole resonance (NQR) studies of 10B and 11B in borate glasses have been accomplished. The data yield values of the quadrupolar parameters (the coupling constant Qcc and the asymmetry parameter ν) that are an order of magnitude more accurate than those obtained from analysis of quadrupolar effects in nuclear magnetic resonance (NMR) spectra. The linewidth of the 11B spectrum (at 1.35 MHz) for crystalline B2O3 is 9.6 ± 0.1 kHz, and the value for vitreous B2 is only 22.3 ± 0.1 kHz. Two 11B responses separated by about 50 kHz are found for vitreous B2O3. They arise from borons in boroxol rings (∼ 85%) and chains of BO3 triangles (∼ 15%). The data are obtained at 77 K with an extremely sensitive regenerative oscillator of the Robinson type. © 1990.