X-ray Emission Spectroscopy

X-ray absorption and emission spectra of carbonate ions in aqueous solution were measured at two concentrations. The signals from the ion were extracted via selective excitation and background subtraction. The obtained spectral shape for the emission of the ion was well explained by DFT calculations.

Resonant inelastic scattering measurements of the conjugated polymer, poly (pyridine-2, 5-diyl) have been performed at the nitrogen and carbon K-edges using synchrotron radiation. For comparison, molecular orbital calculations of the spectra have been carried out with the repeat unit as a model molecule of the polymer chain. The resonant emission spectra show depletion of the π electron bands which is consistent with symmetry selection and momentum conservation rules.

Abstract: The electronic structure of the conjugated polymer, polyaniline, has been studied by resonant and nonresonant X-ray emission spectroscopy using synchrotron radiation for the excitation. The measurements were made on polyaniline and a few doped (protonated) phases for both the carbon and nitrogen contents. The resonant X-ray emission spectra show depletion of the {\ pi} electron bands due to the selective excitation which enhances the effect of symmetry selection rules.

We study the electronic structure and chemical bonding of the SO2 molecule adsorbed on Ni(100) surface using x-ray emission spectroscopy at the O 1s absorption edge. Elemental and symmetry specificities of the method enable us to directly probe surface chemical bonding formed by strong hybridization of O 2p with Ni 3d orbital. Contrary to the expected π bonding due to strong π acceptor character of the SO2 molecule, we find electronic structures with both σ and π characters just below the Ni Fermi level. The details of this complicated surface chemical bonding are discussed using a calculation based on density-functional theory.

Ark 564 (z=0.0247) is an X-ray bright NLS1. By using advanced X-ray timing techniques, Legg et al. (2012) discovered an excess of "delayed" emission in the hard X-ray band (4-7.5 keV) following about 1000 seconds after "flaring" light in the soft X-ray band (0.4-1 keV). We report on the X-ray spectral analysis of eight XMM-Newton and one Suzaku observation of Ark 564. High-resolution spectroscopy was performed with the RGS in the soft X-ray band, while broad-band spectroscopy was performed with the EPIC-pn and XIS/PIN instruments. We analysed time-averaged, flux-selected, and time-resolved spectra. Despite the large variability in flux, the broad band spectral shape of Ark 564 is not dramatically varying and can be reproduced either by a superposition of a power law and a blackbody emission, or by a Comptonized power law emission model. High resolution spectroscopy revealed the presence of ionised gas along the line of sight at the systemic redshift of the source, with a low column density and a range of ionisation states. Broad band spectroscopy revealed a very steep intrinsic continuum and a rather weak emission feature in the iron K band; modelling this feature with a reflection component requires the presence of highly ionised gas. Either a reflection-dominated or an absorption-dominated model are able to well reproduce the time-averaged data from a statistical point of view, in both cases requiring contrived geometries and/or unlikely physical parameters. Finally, through time-resolved analysis we spectroscopically identified the "delayed" emission discovered by Legg et al. (2012) as a spectral hardening above ~4 keV; the most likely interpretation for this component is reprocessing of the "flaring" light by gas located at 10-100 r_g from the central supermassive black hole and so hot to be able to Compton upscatter the flaring intrinsic continuum emission.

Recently, the interest in nanolaminated ternary Mn+ 1AXn denoted 211, 312, and 413, where n= 1, 2, and 3, respectively carbides and nitrides, so-called MAX phases, has grown significantly. Here, M is an early transition metal, A is ap element, usually belonging to the groups IIIA and IVA, and X is either carbon or nitrogen.

Nanocomposites comprise materials with two or more phases for which at least one has nanometer-size crystallites. 1 Carbon-based nanocomposites of nanocrystalline metal carbides (nc-MCs) embedded in an amorphous carbon (aC) matrix, are materials with inherent design possibilities for applications utilizing mechanical, tribological, and/or electrical properties.