Applicability of the Névot-Croce factor in analysis of X-ray reflection from a rough surface

Usability of the Névot-Croce (NC) formula for calculation of the reflectivity from a surface with high-frequency roughness is critically analyzed. First, the necessary conditions of the NC factor applicability are identified quantitatively in the limiting case of vanishingly small correlation length of roughness. Second, the conditions are established, when the nonzero correlation length of real surface roughness can be reckoned as vanishingly small. Third, these conditions are compared with the experimental values of the correlation length of high-frequency roughness. The final conclusions concerning applicability of the NC formula for hard X-ray to extreme ultraviolet radiation are formulated.