Surface acoustic waves (SAWs) are excited on the GaAs (001) surface by using interdigital transducers, designed for frequencies of up to 900 MHz. The emitted phonons with wavelengths down to 3.5 μm are visualized and characterized by combined x-ray diffraction techniques. Using stroboscopic topography, the SAW emission of a parallel and a focusing transducer geometry are imaged. High-resolution x-ray diffraction profiles show up to 12 phonon-induced satellite reflections besides the GaAs (004) reflection, with a width of 9 arcsec each. The diffraction pattern is simulated numerically, applying the kinematical scattering theory to a model crystal. From fits to measured diffraction profiles at different excitation voltages, the SAW amplitudes were calculated and found to be in the sub-nm range.
Anomalous X-ray Diffraction (AXD) methods were used to determine the hydration structure of Y 3+ in a 3.5 m solution of yttrium chloride in water. Data were gathered at two wavelengths below the absorption edge of Y 3+ . The data were corrected for attenuation, inelastic scattering and background and container scattering. They were then renormalized and put on an absolute scale of electron units. Fourier transformation of the results provided information on the Y 3+ hydration. It is found that the short range order around Y 3+ is well established with two well-defined hydration shells. The first, with Y 3+ ‚‚‚H 2 O centered at around 2.30 Å contains 8 water molecules, and the second with Y 3+ ‚‚‚O and Y 3+ ‚‚‚Clis centered at 4.77 Å. The results are in excellent agreement with a recent EXAFS+XANES study. Moreover, it can be shown that the contributions to the first hydration shell from O and H can be resolved in to two peaks, with maxima at 2.28 and 2.95 Å respectively. However, it is not possible to accurately determine coordination numbers for these Y 3+ ‚‚‚O and Y 3+ ‚‚‚H correlations independently due to the approximate nature of the calculations.
The diffuse x-ray scattering and small-angle neutron scattering of a Pt-47 at. % Rh single crystal aged at 923 K were measured to determine the local atomic arrangement. The separated short-range order scattering including the small-angle scattering range showed weak intensity modulations, with the maximum at 1 1 2 0 positions, thus indicating the presence of local order. In contrast to short-range order scattering, size-effect scattering is already well visible in the raw data, in spite of the small difference of 3% in the atomic sizes. Size-effect scattering is mainly due to Rh-Rh displacements.
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