Solid-State 17O Nuclear Magnetic Resonance Spectroscopy Without Isotopic Enrichment: Direct Detection of Bridging Oxygen in Radiation Damaged Zircon

Protocols are presented for obtaining natural abundance O-17 magic angle spinning and static NMR spectra in the solid state. Rotor-assisted population transfer (RAPT), Carr-Purcell-Meiboom-Gill (CPMG) echo trains and cross-polarisation (CP) are all used to obtain spectra of sites with large as well as small electric field gradients in proton and non-proton containing inorganic materials. Spectra are of sufficient quality to obtain the typical NMR parameters by standard fitting of the spectra. The protocol is then applied to identifying the changes that accompany radioactive decay in zircon (ZrSiO4) where enrichment is impossible. The O-17 NMR spectra of a partially metamict zircon sample clearly show evidence of bridging oxygens being produced as a consequence of radiation damage. The spectra have been acquired at moderate magnetic fields over periods typically of 60 h (I weekend) and it is concluded that a 'routine' overnight 110 experiment of 15 h at high field (e.g. 21 T) may well be possible. (C) 2004 Elsevier Inc. All rights reserved.