Complete determination of the reflection coefficient in neutron specular   reflection by absorptive non-magnetic media
  An experimental method is proposed which allows the complete determination of the complex reflection coefficient for absorptive media for positive and negative values of the momenta. It makes use of magnetic reference layers and is a modification of a recently proposed technique for phase determination based on polarization measurements. The complex reflection coefficient resulting from a simulated application of the method is used for a reconstruction of the scattering density profiles of absorptive non-magnetic media by inversion. 
H. Leeb, H. Groetz, J. Kasper, and R. Lipperheide