Affiliations: [a] Neutron Scattering Division, Oak Ridge National Lab, Oak Ridge, Tennessee, USA | [b] Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China | [c] Center for Nanophase Materials Sciences, Oak Ridge National Lab, Oak Ridge, Tennessee, USA | [d] Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee, USA
Note: [1] The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.
Abstract: Neutron reflectometry experiments infer the variation of the scattering length density of a smooth planar film as a function of depth averaged over the lateral dimensions of the sample from the intensity of a neutron beam reflected by the sample. Because the phase information of the neutron wave function is not preserved by an intensity measurement, most analyses rely on comparisons of data to predictions from models. Such comparisons do not provide unique solutions and can yield erroneous conclusions. A real-world example is provided. We show that in some limited cases, measurements of a sample immersed in the vapor and liquid phases of Helium may improve model selection.
