Sr RAXR spectra measured using a flow-through transmission cell containing 1 mM and 100 mM SrCl2 solutions [(a) and (c), respectively], at q = 0.5 Å−1 (L = 1.6 r.l.u.). The measured reflectivity (Rmeas) is normalized to the non-resonant reflectivity calculated using the best-fit model to the CTR data determined previously (Park et al., 2006; Lee, Park et al., 2010) (Rcalc), without considering linear absorption by solution species or resonant effects by Sr at the interface. The calculated and measured X-ray absorption spectra through the 1 mM and 100 mM solutions, respectively, are also plotted for comparison. The spectra after correction for the solution absorption are shown in (b) and (d), respectively, and are compared with that calculated based on the best-fit model of the RAXR data measured previously using a thin-film cell (Park et al., 2006; Lee, Park et al., 2010) (short-dashed line). The data are plotted using a non-resonant amplitude normalization (Park & Fenter, 2007) (= |Ftot/FNR|2, where Ftot and FNR are the total and non-resonant structure factor, respectively).