XANES

About: XANES is a research topic. Over the lifetime, 7737 publications have been published within this topic receiving 188032 citations.

Structure of the water ice surface studied by x-ray absorption spectroscopy at the O K-edge

Abstract: Vapor-deposited H2O ice films grown between 38 and 150 K under ultrahigh vacuum conditions have been investigated using near-edge x-ray absorption fine structure (NEXAFS) spectroscopy at the oxygen K-edge, in conventional mode—which is bulk sensitive-, and using the photon-stimulated desorption mode (PSD-NEXAFS), which is surface sensitive. By recording simultaneously those two signals, we have evidenced the differences between the surface and bulk electronic and atomic structures, for both amorphous porous ice condensed at 40 K and crystalline ice condensed at 150 K. We have also followed the bulk and surface evolutions of an amorphous ice film annealed from 38 to 147 K. A steep change in the local atomic structure of the bulk is observed, likely related to the high-density amorphous ice→low-density amorphous ice phase transition between 38 and 55 K. We have shown that the surface of crystalline ice is well ordered, but this order is different from that of the bulk. We have evidenced that the H2O–H2O int...

Chemical and Mechanical Properties of ZDDP Antiwear Films on Steel and Thermal Spray Coatings Studied by XANES Spectroscopy and Nanoindentation Techniques

Abstract: X-ray Absorption Near Edge Structure (XANES) has been used to characterize the chemistry of tribochemical wear pads generated from a paraffinic base oil with a zinc-dialkyl-dithiophosphate additive on steel surfaces and high-velocity oxygen fuel (HVOF) thermal spray coatings. The phosphorus K- and L- edge XANES spectra show that the tribofilms formed on steel and the HVOF coatings have the same chemical nature. Also, mechanical properties of these tribofilms were examined by nanoindentation techniques using both Hysitron and Interfacial Force Microscopy (IFM) instruments. The elastic moduli extracted from indentation force-displacement (f-d) curves have demonstrated that tribofilms on steel and HVOF coatings have similar surface topography and mechanical properties.

Intrinsic charge transfer gap in NiO from Ni K-edge x-ray absorption spectroscopy

Abstract: Pre-edge features in x-ray absorption spectroscopy contain key information about the lowest excited states and thus on the most interesting physical properties of the system In transition-metal oxides they are particularly structured but extracting physical parameters by comparison with a calculation is not easy due to several computational challenges By combining core-hole attraction and correlation effects in a first-principles approach, we calculate $\text{Ni}\text{ }K$-edge x-ray absorption spectra in NiO We obtain a striking parameter-free agreement with experimental data and show that dipolar pre-edge features above the correlation gap are due to nonlocal excitations largely unaffected by the core hole We show that in charge transfer insulators, this property can be used to measure the correlation gap and probe the intrinsic position of the upper Hubbard band