Membrane Structure Characterization Using Variable-Period X-Ray Standing Waves
- Zhang, Ruitian
- Itri, Rosangela
- Caffrey, Martin
DOIAbstract
AbstractThe variable-period x-ray standing wave (XSW) technique is emerging as a powerful tool for studying membrane structure. However, two significant problems arise when the method is used to characterize membranes of thickness dL<100Å. First, the surface roughness, σr, of the supporting reflecting mirror convolutes with the intrinsic half-width of the marker atom distribution in the membrane, σin, and contributes to an apparent half-width, σ, which is measured in the XSW experiment. Here we show how the latter terms are related quantitatively [σin=(σ2−σr2)1/2], such that rough mirrors give rise to larger marker atom distribution widths, σ, and how the required quantity σin can be determined in the XSW measurement. Second, when the mean ...
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