Investigation of phase transitions in ammonium nitrate by nitrogen–15 nuclear magnetic resonance

Abstract Exploratory Nitrogen-15 nuclear magnetic resonance (NMR) studies of ammonium nitrate (AN) have been undertaken using both conventional and magic angle spinning (MAS) methods. The chemical shift anisotropy is measured by two different methods at room temperature, and a precise measurement of the difference in isotropic chemical shift occurring at the phase transition IV to III is reported. Finally, the activation energy for the motion of both ions in the room temperature phase are obtained. No evidence in discontinuity of nitrogen relaxation times across the phase boundary at 32°C was observed.