Methyl tunnelling in α-crystallised toluene by inelastic neutron scattering: temperature and pressure effects

Abstract
The methyl tunnelling in alpha -crystallised toluenes C6H5CH3 and C6D5CH3 has been studied by high-resolution inelastic neutron scattering. Two tunnel peaks are measured, corresponding to the two inequivalent methyl groups of this crystalline structure. Their frequencies change when deuterating the benzene ring. They are found to exhibit different temperature and pressure (up to 4.6 kbar) effects. All the collected data lead to the determination of two potential models for the methyl group rotation.