text: The ridges enhance the quantum reflection from the surface, reducing the effective constant  of the van der Waals attraction of atoms to the surface. Such interpretation leads to the estimate of the reflectivity
  where  is width of the ridges,  is distance between ridges,  is grazing angle, and  is wavenumber and  is coefficient of reflection of atoms with wavenumber  from a flat surface at the normal incidence. Such estimate predicts the enhancement of the reflectivity at the increase of period ; this estimate is valid at . See quantum reflection for the approximation (fit) of the function .