Phonon dispersion in an α-perylene-d12 crystal at 10 K

Phonon dispersion curves for the 24 external and some of the internal modes in α-perylene-d12 (C20D12) are measured at 10 K for the [ξ00], [0ξ0], and [00ξ] directions by coherent inelastic neutron scattering and Raman scattering. Calculations are performed with a semi-rigid-molecule-model, based on well-known 6-exp-potential functions. The agreement between measurements and calculations is satisfactory. Because of strong mode coupling the identification of the character of the closely neighbouring phonons is often not unique. (author)