Neutron spectroscopy of anilinium bromide

The phase transition from the orthorhombic high temperature phase (I) to the monoclinic low temperature phase (II) in anilinium bromide which occurs at Tsub(c)=296.9 K was studied by incoherent inelastic neutron scattering. Time-of-flight data were obtained from an hydrogenated C6H5NH3Br and partially deuterated samples (C6D5NH3Br and C6H5ND3Br) below and above the transition temperature. Phonon frequency distributions in the range of the intermolecular vibrations were derived from the spectra. The analysis of the quasielastic line revealed substantial broadening. The interpretation lead to reorientational jump processes in the orthorhombic phase (I) and - with a mardedly diminished rate - in the monoclinic phase (II). The activation energies were estimated for both phases. (orig.)