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Published February 1989 | public
Journal Article

Quantitative NMR studies of water in silicate glasses


The state of water in volcanic and synthetic silicate glasses is characterized by a number of different solid state NMR techniques. ^1H solid echo NMR is used to quantitate total water contents reliably down to levels of 0.1 wt%. High-speed ^1H magic-angle spinning NMR can be used to obtain relative species concentrations of OH and H_2O groups in glasses free from paramagnetic impurities. Similar results are obtained from deuterium quadrupolar echo NMR difference spectroscopy, utilizing the different spin-lattice relaxation times of OD and D_2O species. The results demonstrate that the percentage of water present in the form of molecular H_2O species increases with increasing total water content. The H_2O groups are anisotropically constrained, but undergo 180° flips about the bisector axis at rates greater than 10^5 s^(−1). The hydrous species are not clustered and are subjected to a distribution of hydrogen bonding strengths. A distribution function of O-D···O distances obtained from infrared results, shows good compatibility with the experimental ^2H NMR lineshapes. The relative merits of the different experimental approaches are discussed in detail.

Additional Information

© 1989 Elsevier Science Publishers B.V. Received 6 June 1988. Accepted 4 July 1988. We thank our collaborators Drs. L.A. Silver (Caltech), T.R. Stanton, and J. Holloway (Arizona State University) for preparing and characterizing the samples. The NMR experiments were carried out at the Southern California Regional NMR Facility, supported by NSF grant CHE 84-40137. E.M.S. acknowledges additional support by NSF grant EAR 84-17434 and EAR 86-18229. We thank the Donors of the Petroleum Research Fund, administered by the American Chemical Society, for partial support of this research (grant number 17737-AC2). Caltech Division of Geological and Planetary Sciences Contribution number 4655.

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