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The x-ray standing waves generated by dynamical Bragg diffraction were used to directly measure lattice locations of trace elements within and at the surface of a mineral single crystal. These high-precision measurements were made on natural Iceland spar calcite cleaved along the (1014) plane and reacted with a dilute aqueous lead solution. Within the bulk(More)
The adsorption of selenite ions (SeO~-) from a dilute aqueous solution onto a freshly-cleaved calcite (1014) surface was studied with the X-ray standing wave (XSW) technique. The complex ion SeO z-is found to selectively adsorb at the CO~ site via ionic exchange, forming a two-dimensional solid-solution of the form Ca(SeO3)x(CO3) 1 x at the interface. The(More)
Atomic-scale study of ion incorporation at calcite surface using synchrotron X-ray m e t hods Likwan Cheng Understanding the structure of impurity i ons incorporated at the surfaces of ionic crystals is of both fundamental and practical signiicance. The impurity acts as an atomic probe, and the structural perturbation it induces on a surface reveals the(More)
The surface structures of the (6 x 2), c(8 x 4) and (5 × 1) phases of Sn/Si(001) were studied using the X-ray standing wave technique. Using the (004) and (022) Bragg reflections, we find that the (6 x 2) and c(8 × 4) phases are composed of highly buckled Sn-Sn ad-dimers located 1.58 i above the bulk-like Si(004) surface atomic plane. The Sn atoms occupy(More)
This contribution reports the first X-ray standing wave structural characterization of self-assembled NLO-active chromophoric multilayers (SAMs). These siloxane-based self-assembled stilbazolium multilayers are intrinsically acentric and exhibit very large second-order nonlinear optical responses. The locations of bromide ions within the SAMs were precisely(More)
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