Figure 3. Integral photoelectron yield and Fourier power spectra showing the structure of the Pt-Cr-Si bi-layer X-ray mirror.

(a) Measured integral photoelectron yield as a function of the wavevector transfer Q of the incident wave at 10 keV (circles) and fit to Eq. 5 corresponding to photoelectron yield of a thick Pt mirror (green solid line). The inset shows magnified region above the critical angle where the Kiessig fringes due to the layered structure of the mirror are clearly observed. (b) Differential photoelectron yield (circles, Y-error bars and solid line) obtained as the difference between the experimental data and the fit in (a). The differential yield is plotted as a function of the real part of Q₁, the wavevector transfer inside the Pt layer. (c) Forier power spectrum (circles, solid line) of the differential yield (b) showing peaks corresponding to thicknesses of individual layers (Δ₁ and Δ₂ and their sum. (d) Fourier power spectra (circles, solid lines) obtained at different photon energies (shifted for clarity).