XAS spectra measured on GaAs powder, simultaneously, through the As Kα, Ga Kα and absorption channels at the As K-edge. (a) Normalized XANES. (b) Fluorescence EXAFS spectra compared with absorption EXAFS. The noise-filtered 1/Ga Kα data are also shown (full green line). The FT filter cut-offs are k = 0–14 Å−1 and R = 0–10 Å. (c) The FT moduli of the EXAFS spectra (k = 3–12.4 Å−1, Hanning window). (d) The first-shell EXAFS obtained by the back FTs (R = 1.6–2.6 Å). Lower: As Kα (blue), 1/Ga Kα (green), and As Kα/Ga Kα (red). Middle: As Kα and 1/Ga Kα scaled to the standard in the low-k region. Upper: As Kα/Ga Kα data scaled to the standard by ×1.12.