where R is the reflectivity and ν ν is the relative phase of the interfering beams. The characteristic shape of Y p can be used to derive precise structural information about the surface atoms because the two parameters f H (coherent fraction) and P H (coherent position) are directly related to the Fourier representation of the atomic distribution function. Therefore, with a sufficiently large number of Fourier components being measured, XSW data can be used to establish the distribution of the different atoms in the unit cell (XSW imaging).