Dynamics of the modulated crystal smectic B phase of 50.7 by neutron scattering experiments

The cooperative nature of the molecular motions in the crystal smectic B and smectic G phases of 50.7 have been investigated using coherent neutron scattering from a fully deuterated sample. It is concluded that the incommensurable transverse modulation of the smectic B layers, which develops as the smectic G phase is approached, is a static deformation of the layers. New excitations in the energy spectrum should therefore be associated with the layer modulation. Reasons why such excitations were not observed are discussed Etude de la nature cooperative du mouvement moleculaire dans les phases smectique B et smectique G sur un echantillon completement deutere. La modulation transverse incommensurable de la couche smectique B, qui croit lorsqu'on approche de la phase smectique G, est une deformation statique des couches. Dans le spectre d'energie de nouvelles excitations doivent etre associees a la modulation des couches