Resolution Function for Two-Axis Specular Neutron Reflectivity

The resolution function for specular neutron reflectivity measurements of flat samples is calculated. The results are also applicable to some X-ray reflectivity set-ups. In a basic approach, the contributions of the wavelength spread and the angular divergence are calculated. The method of combining these contributions is discussed. These calculations are compared with some measured reflectivity curves. The calculations are checked with an analytical beam analysis method that takes directly into account the coupling between the angle, position and wavelength of the neutrons.