(a) The real parts of the refractive indices, δ, for an Si substrate, polystyrene (PS), SEBS films and water at the Si K absorption edge. They were calculated from reported values of the anomalous scattering factors and densities. For SEBS, the density of the present sample was determined from the critical angle measurements at Cu Kα1. (b) Reflectivity curves calculated for a model sample having 50 nm of SEBS film on an Si substrate. The refractive indices are taken from the above.