Phase determination and inversion in specular neutron reflectometry

We present results testing the experimental feasibility of recently discovered solutions of the dynamical phase problem for specular reflection. Using layers of Cu, Ni, and Mo as references, the real and imaginary parts of the complex reflection amplitude were measured from neutron reflectivities for an asymmetric composite film consisting of deuterated polystyrene and Si. The reflection amplitude was also measured from neutron reflectivity without references for a symmetric deuterated polystyrene film. These amplitudes were inverted using the Gel'fand-Levitan-Marchenko equation to produce scattering length density profiles for the films studied. The inverted profiles compared reasonably well to the expected potentials. We conclude that such methods are practical with current instrumentation. (C) 1998 Published by Elsevier Science B.V.