X-Ray Reflectivity and Diffraction Studies of Liquid Surfaces and Surfactant Monolayers

Abstract

The structure of matter on a molecular length scale can be revealed by diffraction studies using radiation with wavelength in the Ångstrøm region. If the radiation couples weakly to the scattering objects, as is the case for neutrons and X-rays (but not for electrons), the interpretation of the diffraction pattern in terms of the underlying structure becomes particularly simple and reliable due to the validity of the Born approximation, which in this context is also called kinematical diffraction. On the other hand, if the coupling is weak, the beam has to be sufficiently intense and/or the sample must be of sufficient size to obtain an accurate diffraction pattern within a reasonable time. In a surface structure the number of diffracting atoms, confined within a nanometer thick surface layer, is comparatively small.