Search results for "Spectroscopy"

Intrinsic absorption threshold of stishovite and coesite

2004

Abstract The optical absorption spectra of the small mono-crystals samples of stishovite and coesite were studied at first. The intrinsic absorption threshold of stishovite is determined at 8.75 eV, being probably, highest in the family of different crystalline polymorph modifications of silicon dioxide. The absorption spectrum of stishovite is independent of temperature (studied in the range 290–450 K). The intrinsic absorption threshold of coesite mono-crystal situated near 8.6 eV at 293 K, coincides within experimental errors with that of α-quartz crystal, and depends on temperature, as used to be for the tetrahedron structured silicon dioxide crystalline modifications. A broad absorptio…

EXAFS and XANES Studies of CoxMg1−xO Solid Solutions Using a Laboratory EXAFS Spectrometer

1993

Studies of the local electronic structure and the short-range order in solid solutions CoxMg1−xO with x varying from 0.02 to 1.00 are carried out on the CoK-edge X-ray absorption spectra using a laboratory EXAFS spectrometer. A non-monotonous change of the CoO distance in the first coordination shell with a bent at about x = 0.5 is established. The second coordination shell of cobalt is formed by cobalt and magnesium atoms with a distribution close to a statistical one. [Russian Text Ignored.]

First glimpse of the soft x-ray induced excited spin-state trapping effect dynamics on spin cross-over molecules.

2013

The dynamics of the soft x-ray induced excited spin state trapping (SOXIESST) effect of Fe(phen)(2)(NCS)(2) (Fe-phen) powder have been investigated by x-ray absorption spectroscopy (XAS) using the total electron yield method, in a wide temperature range. The low-spin (LS) state is excited into the metastable high-spin (HS) state at a rate that depends on the intensity of the x-ray illumination it receives, and both the temperature and the intensity of the x-ray illumination will affect the maximum HS proportion that is reached. We find that the SOXIESST HS spin state transforms back to the LS state at a rate that is similar to that found for the light induced excited spin state trapping (LI…

Crystallographic and (spectro)electrochemical characterizations of cobalt(II) 10-phenyl-5,15-di-p-tolylporphyrin

2021

International audience; The synthesis, cyclic and rotating disk electrode voltammograms, UV-visible absorption and Xray diffraction analyses of cobalt(II) 10-phenyl-5,15-dip -tolylporphyrin (1-Co) are described. 1-Co was crystallized by slow diffusion of n-hexane into a concentrated CH2Cl2 solution. X-ray diffraction analyses reveals porphyrin aromatic cycle stacking in the crystal, C-H•••π interactions of the CH2Cl2 solvent with the π-system of one tolyl group and Co(II)•••π (porphyrin ring) interactions. The abstraction of 1.0 F/mol during the electrolysis at the first oxidation potential was followed by spectroelectrochemistry. It leads to the Co(II) → Co(III) transformation rather than …

Preparative and spectroscopic features of ferricenium tetrachloroferrate(III). Interconversion to diferricenium ?-oxo-bis[trichloroferrate(III)]

1985

Ferricenium tetrachloroferrate(III)(1), one of the more frequently cited ferricenium salts, has recently attracted biomedical interest because of its pronounced antineoplastic activity against Ehrlich ascites murine tumor. In this paper, synthetic methods are reinvestigated in an effort to prepare pure(1) free from a common contaminant, diferriceniumμ-oxo-bis(trichloroferrate)(3). The oxodiferrate, or mixtures of this salt with(1), can readily be converted into pure(1) under acidic conditions. Conversely, dimerization of(1) with participation of water to give the oxodiferrate(3) is brought about by recrystallization of the former from moist acetonitrile/methanol in the presence of base; thi…

Diphenoxido‐Bridged Co II and Zn II Complexes of Tripodal N 2 O 2 Ligands: Stabilisation of M II ‐Coordinated Phenoxyl Radical Species

2010

Three new tripodal ligands with an N 2 O 2 donor set, namely 2-tert-butyl-6-({(2-hydroxybenzyl)[2-(2-pyridyl)ethyl]amino}-methyl)-4-methylphenol (H 2 L 1 ), 2-tert-butyl-6-({(2-hydroxybenzyl)[2-(2-pyridyl)ethyl]amino}methyl)-4-methoxy-phenol (H 2 L 2 ) and 2-tert-butyl-6-({[2-(dimethylamino)ethyl]-(2-hydroxybenzyl)amino}methyl)-4-methoxyphenol (H 2 L 3 ) have been synthesised. Treatment of the ligands with Co-(CH 3 CO 2 ) 2 ·4H 2 O or [Zn(H 2 O) 6 ][ClO 4 ] 2 in the presence of Et 3 N provides the corresponding Co II and Zn" complexes of composition [M II 2 (L 1 ) 2 ] [M = Co (1) (single-crystals are a solvate with the composition [Co II 2 (L 1 ) 2 ]·2CHCl 3 , i.e. 1·2CHCl 3 ); M = Zn (2)],…

Analysis of the U L3-edge X-ray absorption spectra in UO2 using molecular dynamics simulations

2017

This work was supported by a grant from the Swiss National Supercomputing Centre (CSCS) under the project ID s444. The resource allocation within the PSI share at CSCS and on the PSI compute cluster Merlin4 is also acknowledged. D. B. is grateful for a fellowship within the Sciex-NMS programme. A. K. was supported by Latvian Science Council Grant no. 187/2012.

Some aspects of the solid state physics of yellow arsenic

1996

Luminescent osmium(II) bi-1,2,3-triazol-4-yl complexes: photophysical characterisation and application in light-emitting electrochemical cells

2016

The series of osmium(II) complexes [Os(bpy)3-n(btz)n][PF6]2 (bpy = 2,2’-bipyridyl, btz = 1,1’-dibenzyl-4,4’-bi-1,2,3-triazolyl, 1 n = 0, 2 n = 1, 3 n = 2, 4 n = 3), have been prepared and characterised. The progressive replacement of bpy by btz leads to blue-shifted UV-visible electronic absorption spectra, indicative of btz perturbation of the successively destabilised bpy-centred LUMO. For 4, a dramatic blue-shift relative to the absorption profile for 3 is observed, indicative of the much higher energy LUMO of the btz ligand over that of bpy, mirroring previously reported data on analogous ruthenium(II) complexes. Unlike the previously reported ruthenium systems, heteroleptic complexes 2…

Electronic signature of the instantaneous asymmetry in the first coordination shell of liquid water

2013

Interpretation of the X-ray spectra of water as evidence for its asymmetric structure has challenged the conventional symmetric nearly-tetrahedral model and initiated an intense debate about the order and symmetry of the hydrogen bond network in water. Here, we present new insights into the nature of local interactions in water obtained using a novel energy decomposition method. Our simulations reveal that while a water molecule forms, on average, two strong donor and two strong acceptor bonds, there is a significant asymmetry in the energy of these contacts. We demonstrate that this asymmetry is a result of small instantaneous distortions of hydrogen bonds, which appear as fluctuations on …