RESUMO
Empirical potential structure refinement (EPSR) has been used to build experimentally consistent models of a range of electrolyte solutions containing di- and trivalent cations: Cu(ClO4)2 at concentrations of 0.5 and 2.0 m, and Cr(NO3)3, YCl3 and LaCl3 at a concentration of 1.0 m. The resulting models are used to investigate the perturbation of these electrolytes on the pair distribution and triplet angle correlations between solvent water molecules, compared with those found in the pure solvent. The results elucidate the differences that derive from the reflected range of highly structured local cation environments and provide a complementary viewpoint on the hydration shell geometries.
RESUMO
The design and performance of the microfocus spectroscopy beamline at the Diamond Light Source are described. The beamline is based on a 27 mm-period undulator to give an operable energy range between 2 and 20.7 keV, enabling it to cover the K-edges of the elements from P to Mo and the L(3)-edges from Sr to Pu. Micro-X-ray fluorescence, micro-EXAFS and micro-X-ray diffraction have all been achieved on the beamline with a spot size of approximately 3 microm. The principal optical elements of the beamline consist of a toroid mirror, a liquid-nitrogen-cooled double-crystal monochromator and a pair of bimorph Kirkpatrick-Baez mirrors. The performance of the optics is compared with theoretical values and a few of the early experimental results are summarized.