71Ga and 69Ga nuclear magnetic resonance (NMR) spectra have been obtained for β-Ga2O3 at magnetic fields of 11.7 and 7.0 T with a combination of static and spinning samples and using echo techniques. Isotropic chemical shifts and well constrained electric field gradient (EFG) tensors were measured for the GaIV and GaVI sites in β-Ga2O3 and are reported for the first time. Due to its high quadrupolar coupling constant the GaIV site in β-Ga2O3 is only resolved in static conditions. Analysis of spectral discontinuities obtained for different isotopes and magnetic field strengths and a method of readily obtaining very broad spectra without point by point acquisition demonstrate an approach that should be very useful in constraining the chemical shifts and quadrupole parameters involved in solid-state gallium NMR spectra.

The drying of a limestone block was studied by analysing one-dimensional projections (profiles) and three-dimensional (3D) NMR images as well as free induction decay (FID), as a function of the amount of water remaining in the sample at various stages of the drying process. From these results, the water repartition in the sample stays continuous and fairly uniform down to a water content W of the order of 2% in weight of water per weight of rock. However, at the end of the drying, for W<2%, water is no longer uniformly distributed. The remaining water is concentrated in the centre of the block where the NMR signal is intense, whereas in the surrounding region the NMR signal is drastically weaker. This is the first report on drying of a porous stone monitored by NMR imaging through to its late stage. These first results show spatial compartmentation and modification of the physicochemical state of the protons during the drying, which would be difficult to observe with other techniques. The authors suggest a two-compartment model which is consistent with images and profiles.

The authors have studied the cubic-to-tetragonal structural phase transition in RbCaF3 at atmospheric and high pressures by nuclear magnetic resonance techniques. The spin-lattice relaxation time T1 and the quadrupole coupling constant vQ have been measured near the phase transition at 13350 and 5400 bar, and thus the pressure dependence of the transition temperature Tc has been deduced. They compare their results with those concerning other perovskites. A two-dimensional Fourier-transform method based on the quadrupole interaction has been used to show phase coexistence at P=1 bar. At high pressure the authors have developed a method based on pulse-length excitation to detect any phase coexistence. Finally they discuss the change of the phase transition with increasing pressure.