Surface Investigation by Neutron Reflection

Abstract

ABSTRACTSeveral phenomena analogous to those observed in classical optics, such as reflection, refraction and interference, are also observed with slow neutrons. Information on surface properties, described by a refractive index profile, can be extracted from reflection experiments. This information is similar to that obtained by X-ray reflection. However, there are some instances where the new neutron method provides a distinct advantage. The refractive index is related to the scattering length density, a parameter which describes the neutron-matter interaction. Owing to the magnetic interaction, magnetic materials have a neutron spin dependent refractive index, and a critical reflection of polarized neutrons is a particularly sensitive probe of surface magnetism. On the other hand, in contrast to X-rays, neutron scattering length values vary randomly from element to element. Isotopic substitution can then produce a contrast in the scattering length density. Of particular importance is the large difference between hydrogen and deuterium. This is a distinct advantage for studiyng many problems in surface chemistry, particularly in the polymer field.