[en] Extended x-ray absorption fine-structure (EXAFS) data collected in the fluorescence mode are susceptible to an apparent amplitude reduction due to the self-absorption of the fluorescing photon by the sample before it reaches a detector. Previous treatments have made the simplifying assumption that the effect of the EXAFS on the correction term is negligible, and that the samples are in the thick limit. We present a nearly exact treatment that can be applied for any sample thickness or concentration, and retains the EXAFS oscillations in the correction term

[en] A pair distribution function (PDF) analysis of temperature-dependent x-ray diffraction measurements from UCu₄Pd is presented. Fits to the displacement parameters (u₂'s) with a Debye model show better agreement with a model that includes 25% of the Pd atoms on 16e (Cu) sites. In addition, significant non-thermal disorder is observed in the Cu environment, in contrast to previous measurements of local order in the U-Cu pairs

[en] The Cp*₂Yb(L) class of compounds, where Cp* = pentamethylcyclopentadienyl = C₅Me₅ and L is either a 1,4-diazabutadiene or bipy = 2,2'-bipyridine related ligand, have provided excellent analogies to the Kondo state on the nanoscale. Cp*₂Yb(4,4'-Me₂-bipy) furthers this analogy by demonstrating a valence transition as the sample is cooled below 200 K. Here, pair-distribution function (PDF) analysis of x-ray powder diffraction data demonstrate that the Cp*₂Yb(4,4'-Me₂-bipy) molecule is virtually unchanged through the valence transition. However, the molecule's stacking arrangement is altered through the valence transition.

[en] The UCu5-x Pdx system exhibits non-Fermi liquid (NFL) behavior in thermodynamic and transport properties at low temperatures for Pd concentrations 0.9 less than or approximately x less than or approximately 1.5. The local structure around the U, Cu, and Pd atoms has been measured for

[en] The sun exhibits periodic and quasi-periodic variability in its total luminosity, which provides information about its internal structure and dynamics. Variability ranges from a few minutes to many-year time scales, with amplitudes as small as a few ppm in the milliHz band. Extension of this analysis to a large sample of outer stars would be interesting: a panoramic detector such as a CCD could record many stars at once. To meet this objective, a ppm time-series differential precision is required. Laboratory CCD photometric measurements presented here are promising for such an instrument. Normalizing the response from a portion of the CCD area removes most of the individual-frame variability. When a trend attributed to a thermal transient in the CCD dewar is removed, the individual-frame photometric precision is about 0.0001, limited by photoelectron counting statistics. The time-series power spectrum is flat within the desired frequency domain. Analysis of the dimensional stability of the CCD within the same data set indicates better than ppm performance, when first-order bulk motion and magnification changes are removed. 17 refs

[en] The magnetic and electronic properties of non-Fermi liquid UCu_4Pd depend on annealing conditions. Local structural changes due to this annealing are reported from UL_III- and Pd K-edge x-ray absorption fine-structure measurements. In particular, annealing decreases the fraction of Pd atoms on nominally Cu 16e sites and the U-Cu pair-distance distribution width. This study provides quantitative information on the amount of disorder in UCu_4Pd and allows an assessment of its possible importance to the observed non-Fermi liquid behavior

[en] Although Pd/Cu site interchange in the non-Fermi liquid (NFL) material UCu₄Pd has been observed, the relationship between this disorder and the NFL behavior remains unclear. In order to better compare to the UCu_5-xPd_x phase diagram, they report results from Pd K edge x-ray absorption fine structure (XAFS) experiments on this series (x = 0.3-1.5) that determine the fraction of Pd atoms on the nominally Cu (16e) sites, s. They find that for these unannealed samples, s is at least 17% for all the samples measured, even for x < 1.0, although it does climb monotonically beyond its minimum at x = 0.7. These data are compared to changes in the lattice parameter as a function of x

No abstract available

[en] Polarized X-ray absorption fine-structure (XAFS) data are reported for Rh and Ge K edges on antiferromagnetic and spin-glass samples of URh₂Ge₂. Proposed crystal structures have two possible kinds of layers for the Rh and Ge atoms. The XAFS data indicate that each species forms both kinds of layers and therefore the dominant phase has a crystal structure like that of CaBe₂Ge₂

[en] The local structure around Sn dopants in CeCoIn_5-xSn_z has been probed by extended x-ray absorption fine structure (EXAFS) technique. The fit results for both x = 0.12 and x = 0.18 clearly indicate the dopant Sn atoms predominantly occupying the planar In(1) site. These results are consistent with the quasi-two-dimensional electronic properties of CeCoIn₅ and is discussed in relation to the observed bulk properties