“…Specific aspects of measurement geometry in the regime of total external reflection of X-ray is physical basis of low-angle X-ray spectroscopy, diffraction, and reflectometry techniques such as total reflection X-ray fluorescence (TXRF) [3], grazing incidence X-ray fluorescence (GIXRF) [3], grazing emission X-ray fluorescence (GEXRF) [3,9,10], grazing incidence X-Ray diffraction (GIXRD) [11], and the X-ray reflectometry [12]. These techniques are often used to analyze nanolayers, which facilitates determining various properties of sample surfaces, e.g., elemental and chemical composition, morphology, density, thickness, roughness, and depth profile, also by our atomic physics and nanophysics group, in different applications [3,[13][14][15].…”