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.