scholarly journals X-ray Absorption Spectroscopic studies of Single Crystal SrFeO3-δ

2014 ◽  
Vol 70 (a1) ◽  
pp. C1527-C1527
Author(s):  
Shang Hsien Hsieh ◽  
Mukta Vinayak Limaye ◽  
Shashi Bhushan Singh ◽  
Yu Cheng Shao ◽  
Yu Fu Wang ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Single Crystal ◽  
Thermal Hysteresis ◽  
Spectroscopic Studies ◽  
Temperature Dependent ◽  
Zone Method ◽  
Edge Structure ◽  
X Ray ◽  
Length Changes ◽  
X Ray Absorption

We have prepared a high quality single crystal of SrFeO3-δ (δ ~ 0.14) by the floating-zone method to study the electronic and atomic structures using temperature-dependent x-ray absorption near-edge structure (XANES), x-ray linear dichroism (XLD), and extended x-ray absorption fine structure (EXAFS) at the O K-edge, Fe L3,2- and K-edge. Resistivity measurements indicate that the SrFeO2.86 shows an anisotropic behavior, and thermal hysteresis behavior between 70 K and 40 K. The temperature dependent Fe K-edge EXAFS studies shows that the Fe-O bond length changes in ab-plane below transition temperature. The XLD results illustrate that as temperature is reduced from room temperature to below the transition temperature, the preferential occupancy of Fe majority-spin eg orbitals changes from the 3d3z2-r2 to 3dx2-y2, but restore to 3dx2-y2 after thermal hysteresis. Experimental findings suggest that the charge transfer during thermal hysteresis is induced by lattice distortions of the FeO6 octahedra in SrFeO2.86.

Temperature dependent electronic structure of Pr0.67Sr0.33MnO3 film probed by X-ray absorption near edge structure

2014 ◽  
Vol 115 (17) ◽  
pp. 17E116 ◽  
Author(s):  
Bangmin Zhang ◽  
Cheng-Jun Sun ◽  
Jing-Sheng Chen ◽  
T. Venkatesan ◽  
Steve M. Heald ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Temperature Dependent ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

scholarly journals In situ X-ray absorption spectroscopic studies of TiO2 photocatalytic active sites for degradation of trace CHCl3 in drinking water

2021 ◽  
Vol 28 (6) ◽  
Author(s):  
T.-L. Hsiung ◽  
L.-W. Wei ◽  
H.-L. Huang ◽  
H. Paul Wang
Keyword(s):  
Drinking Water ◽  
Photocatalytic Degradation ◽  
Active Sites ◽  
Spectroscopic Studies ◽  
Band Gap Energy ◽  
Disinfection Byproducts ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

Toxic disinfection byproducts such as trihalomethanes (e.g. CHCl3) are often found after chlorination of drinking water. It has been found that photocatalytic degradation of trace CHCl3 in drinking water generally lacks an expected relationship with the crystalline phase, band-gap energy or the particle sizes of the TiO2-based photocatalysts used such as nano TiO2 on SBA-15 (Santa Barbara amorphous-15), TiO2 clusters (TiO2–SiO2) and atomic dispersed Ti [Ti-MCM-41 (Mobil Composition of Matter)]. To engineer capable TiO2 photocatalysts, a better understanding of their photoactive sites is of great importance and interest. Using in situ X-ray absorption near-edge structure (XANES) spectroscopy, the A1 (4969 eV), A2 (4971 eV) and A3 (4972 eV) sites in TiO2 can be distinguished as four-, five- and six- coordinated Ti species, respectively. Notably, the A2 Ti sites that are the main photocatalytic species of TiO2 are shown to be accountable for about 95% of the photocatalytic degradation of trace CHCl3 in drinking water (7.2 p.p.m. CHCl3 gTiO2 −1 h−1). This work reveals that the A2 Ti species of a TiO2-based photocatalyst are mainly responsible for the photocatalytic reactivity, especially in photocatalytic degradation of CHCl3 in drinking water.

scholarly journals X-ray absorption spectroscopic studies of zinc in the N-terminal domain of HIV-2 integrase and model compounds

2002 ◽  
Vol 10 (1) ◽  
pp. 86-95 ◽  
Author(s):  
Martinus C. Feiters ◽  
Astrid P. A. M. Eijkelenboom ◽  
Hans-Friedrich Nolting ◽  
Bernt Krebs ◽  
Fusinita M. I. van den Ent ◽  
...  
Keyword(s):  
Multiple Scattering ◽  
Spectroscopic Studies ◽  
Nmr Structure ◽  
Model Compounds ◽  
Edge Structure ◽  
Nmr Structure Determination ◽  
X Ray ◽  
Major Shell ◽  
Type Factor ◽  
X Ray Absorption

X-ray absorption spectroscopy (XAS), including extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) analysis, has been carried out at the ZnKedge of the N-terminal part of the integrase protein of the human immunodeficiency virus, type 2 (HIV-2), and of some zinc coordination compounds. In the presence of excess β-mercaptoethanol, which was present in the NMR structure elucidation of the protein [Eijkelenboomet al.(1997),Curr. Biol.7, 739–746; (2000),J. Biomol. NMR,18, 119–28], the protein spectrum was nearly identical to that recorded in its absence. Comparison of the XANES of the protein with that of model compounds and literature data permits the conclusion that the Zn ion is four-coordinated. The major shell of the EXAFS provides evidence for a mixed (N or O as well as S) coordination sphere, while the minor shells indicate imidazole coordination. Our approach to the analysis of the EXAFS, including quantification of the imidazole by multiple scattering simulations withEXCURV92, was validated on the model compounds. An important result is that with multiple scattering simulations using restraints on the parameters of the imidazole rings the number of imidazoles and their orientation could be determined. The integrase spectra can be fitted with two sulfur ligands at 2.26 Å (Debye–Waller-type factor 0.009 Å2) and two imidazole ligands with the N atoms at 1.99 Å (Debye–Waller-type factor 0.005 Å2). The XAS-derived geometry is fully consistent with that found in the NMR structure determination and, allowing for the volume contraction due to the temperature difference between the experiments, justifies the restraints applied in the structure calculation (Zn—S and Zn—N distances of 2.3 Å and 2.0 Å, respectively).

LOCAL STRUCTURE OF THE CHARGE ORDERED La0.5Ca0.5MnO3

2000 ◽  
Vol 14 (25n27) ◽  
pp. 2852-2857
Author(s):  
S. AGRESTINI ◽  
N. L. SAINI ◽  
A. LANZARA ◽  
F. NATALI ◽  
A. BIANCONI
Keyword(s):  
Charge Ordering ◽  
Temperature Dependent ◽  
Edge Structure ◽  
X Ray ◽  
Disordered Phase ◽  
Local Lattice ◽  
Jahn Teller ◽  
Lattice Distortions ◽  
X Ray Absorption ◽  
Absorption Measurements

Local lattice of the charge ordered La 0.5 Ca 0.5 MnO 3 has been studied by temperature dependent Mn K-edge x-ray absorption measurements, using fluorescence detection method, to explore how the local lattice distortions are associated with the charge ordering in this system. The x-ray absorption near edge structure (XANES) reveals an abrupt change in the local MnO 6 octahedral geometry across the charge ordering temperature. The extended x-ray absorption fine structure (EXAFS) analysis shows largely distorted MnO 6 octahedra with coexisting Q 3-type and Q 2-type of Jahn-Teller (JT) modes at low temperature in the commensurate charge ordered phase. We find that small JT distortions persist also in the charge disordered phase at high temperature.

scholarly journals Light-Induced Relaxation of Photolyzed Carbonmonoxy Myoglobin: A Temperature-Dependent X-Ray Absorption Near-Edge Structure (XANES) Study

2005 ◽  
Vol 88 (4) ◽  
pp. 2954-2964 ◽  
Author(s):  
A. Arcovito ◽  
D.C. Lamb ◽  
G.U. Nienhaus ◽  
J.L. Hazemann ◽  
M. Benfatto ◽  
...  
Keyword(s):  
Temperature Dependent ◽  
Edge Structure ◽  
X Ray ◽  
Carbonmonoxy Myoglobin ◽  
X Ray Absorption
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