23Na nuclear magnetic resonance spin echo decay spectroscopy of sodium silicate glasses and crystalline model compounds.

摘要: Abstract The possibility of using Hahn spin echo decay spectroscopy for measuring 23Na-23Na dipole-dipole couplings in crystalline solids and glasses is investigated. Although the presence nuclear electric quadrupolar splittings complicates situation compared to case among spin- 1 2 nuclei, experimentally measured second moments lie within approximately 10–20% calculated values, if following conditions are fulfilled: (1) selective excitation central → − transition, (2) restriction analysis short evolution times (2t1 ≤ 200 μs). At longer times, partial suppression spin-exchange term dipolar Hamiltonian due magnetic inequivalencies between interacting nuclei produces substantial differences experimental decays, extent which depends on compound considered. These results signify potential utility 23Na resonance testing distribution Na-Na distances structurally disordered glasses. method shown be applicable sodium silicate glasses, where it reproduces anticipated compositional trends couplings. Details inherent limitations this methodology discussed.