Phonon dispersion curves of ordered phases of T.B.B.A

The lattice dynamics of a deuterated single crystal of T.B.B.A. have been measured by mean of inelastic neutron scattering. The acoustic phonon propagation, specially the transverse mode propagating perpendicularly to the planes of molecules, has been observed in the crystalline phase and in both smectic B and E phases. While the energy of the longitudinal modes varies just a litle in the different phases, the energy of the transverse mode, near the zone boundary, increases in the smectic phases. An attempt of analysis of the phonon width in the smectic phases has been undertaken