Neutron inverse optics in layered materials

Neutron specular reflectivity data obtained with a new grazing angle neutron spectrometer (GANS) from a NiC/Ti-multilayer sample were analyzed and modeled for reconstructing the scattering length density profile as a periodic step potential for the layered material. There is some ambiguity in the results due to the uniqueness problem with missing phase information. For more complex layered materials, there is often insufficient knowledge about the layers to use modeling reconstruction without phase information. In the second part, we present a method in which this problem is solved for diffraction data from lipid multilayers: due to changes in chemistry (isomorphous heavy atom method) the phases are determined directly and therefore the density profile of the lipid bilayer can be uniquely determined.