RAXR spectra of muscovite (001) measured using the flow-through transmission cell at q = 0.49 Å−1 near the Rb K-edge (∼15.2 keV), with three different solutions [3 mM LiCl (green), 3 mM RbCl (red) and 1 mM SrCl2 (cyan)]. The data are plotted without correction for linear absorption. The solid lines through the data points are calculated based on the model-independent analyses of the data (Park & Fenter, 2007). The small modulations in the calculated lines for LiCl and SrCl2 are mostly due to a fitting artifact. The best-fit results indicate that derived RAXR amplitudes are mostly insignificant (0.03 ± 0.02 and 0.04 ± 0.03 Rb/AUC for the LiCl and SrCl2 data, respectively).