Modern NMR Approaches to the State of Water in Glasses

The state of water in volcanic and synthetic silkate glasses is characterized by a number of different modern solid state NMR techniques. ^1H solid echo NMR is used to quantitate total water contents reliably down to levels of 0.1 wt. %. Relative species concentrations of OH and H_2 are obtained either from an analysis of ^1H MAS-NMR spinning sideband patterns or by deuterium quadrupolar echo NMR difference spectroscopy, utilizing the different spin-lattice relaxation characteristics of OD and D_2O species. A distribution function of O-D···O distances, simulated on the basis of infrared results, yields good agreement with the experimental ^2H NMR lineshapes.