Jahn-Teller distortion aroundFe4+inSr(FexTi1−x)O3−δfrom x-ray absorption spectroscopy, x-ray diffraction, and vibrational spectroscopy

2007 ◽  
Vol 76 (17) ◽  
Author(s):  
M. Vračar ◽  
A. Kuzmin ◽  
R. Merkle ◽  
J. Purans ◽  
E. A. Kotomin ◽  
...  
2020 ◽  
Author(s):  
Marta L. Vidal ◽  
Michael Epshtein ◽  
Valeriu Scutelnic ◽  
Zheyue Yang ◽  
Tian Xue ◽  
...  

We report a theoretical investigation and elucidation of the x-ray absorption spectra of neutral benzene and of the benzene cation. The generation of the cation by multiphoton ultraviolet (UV) ionization as well as the measurement of<br>the carbon K-edge spectra of both species using a table-top high-harmonic generation (HHG) source are described in the companion experimental paper [M. Epshtein et al., J. Phys.<br>Chem. A., submitted. Available on ChemRxiv]. We show that the 1sC -> pi transition serves as a sensitive signature of the transient cation formation, as it occurs outside of the spectral window of the parent neutral species. Moreover, the presence<br>of the unpaired (spectator) electron in the pi-subshell of the cation and the high symmetry of the system result in significant differences relative to neutral benzene in the spectral features associated with the 1sC ->pi* transitions. High-level calculations using equation-of-motion coupled-cluster theory provide the interpretation of the experimental spectra and insight into the electronic structure of benzene and its cation.<br>The prominent split structure of the 1sC -> pi* band of the cation is attributed to the interplay between the coupling of the core -> pi* excitation with the unpaired electron<br>in the pi-subshell and the Jahn-Teller distortion. The calculations attribute most of<br>the splitting (~1-1.2 eV) to the spin coupling, which is visible already at the Franck-Condon structure, and estimate the additional splitting due to structural relaxation to<br>be around ~0.1-0.2 eV. These results suggest that x-ray absorption with increased resolution might be able to disentangle electronic and structural aspects of the Jahn-Teller<br>effect in benzene cation.<br>


2007 ◽  
Vol 75 (5) ◽  
Author(s):  
Aline Y. Ramos ◽  
Hélio C. N. Tolentino ◽  
Narcizo M. Souza-Neto ◽  
Jean-Paul Itié ◽  
Liliana Morales ◽  
...  

2009 ◽  
Vol 404 (8-11) ◽  
pp. 1404-1408 ◽  
Author(s):  
Y.T. Tsai ◽  
W.J. Chang ◽  
S.W. Huang ◽  
J.-Y. Lin ◽  
J.Y. Lee ◽  
...  

1996 ◽  
Vol 60 (403) ◽  
pp. 887-896 ◽  
Author(s):  
J. M. Charnock ◽  
P. F. Schofield ◽  
C. M. B. Henderson ◽  
G. Cressey ◽  
B. A. Cressey

AbstractThe advantages of X-ray absorption spectroscopy have been utilized to assess the Cu and Zn ordering in aurichalcite, (Cu5−xZnx)(OH)6(CO3)2. We have examined one hydrozincite sample and three aurichalcite samples in which the Cu:Zn ratios are in the range 1:3 to 2:3. Copper 2p XAS confirms that there is no monovalent copper in aurichalcite and that in each sample the copper might be distributed across more than one metal site. EXAFS, at the Cu and Zn K-edges, shows that the copper atoms preferentially enter the Jahn-Teller elongated, octahedral (M2) and trigonal bipyramidal (M4) sites, with the zinc atoms entering the more regular octahedral (M1) and tetrahedral (M3) site. Substantial solid solution towards the zinc rich region is facilitated by the substitution of copper by zinc on the M2 and M4 sites. This information, not easily obtained by X-ray diffraction, substantially enhances the understanding of the structure of aurichalcite.


2020 ◽  
Author(s):  
Marta L. Vidal ◽  
Michael Epshtein ◽  
Valeriu Scutelnic ◽  
Zheyue Yang ◽  
Tian Xue ◽  
...  

We report a theoretical investigation and elucidation of the x-ray absorption spectra of neutral benzene and of the benzene cation. The generation of the cation by multiphoton ultraviolet (UV) ionization as well as the measurement of<br>the carbon K-edge spectra of both species using a table-top high-harmonic generation (HHG) source are described in the companion experimental paper [M. Epshtein et al., J. Phys.<br>Chem. A., submitted. Available on ChemRxiv]. We show that the 1sC -> pi transition serves as a sensitive signature of the transient cation formation, as it occurs outside of the spectral window of the parent neutral species. Moreover, the presence<br>of the unpaired (spectator) electron in the pi-subshell of the cation and the high symmetry of the system result in significant differences relative to neutral benzene in the spectral features associated with the 1sC ->pi* transitions. High-level calculations using equation-of-motion coupled-cluster theory provide the interpretation of the experimental spectra and insight into the electronic structure of benzene and its cation.<br>The prominent split structure of the 1sC -> pi* band of the cation is attributed to the interplay between the coupling of the core -> pi* excitation with the unpaired electron<br>in the pi-subshell and the Jahn-Teller distortion. The calculations attribute most of<br>the splitting (~1-1.2 eV) to the spin coupling, which is visible already at the Franck-Condon structure, and estimate the additional splitting due to structural relaxation to<br>be around ~0.1-0.2 eV. These results suggest that x-ray absorption with increased resolution might be able to disentangle electronic and structural aspects of the Jahn-Teller<br>effect in benzene cation.<br>


1991 ◽  
Vol 44 (10) ◽  
pp. 1495 ◽  
Author(s):  
RC Bott ◽  
DS Sagatys ◽  
DE Lynch ◽  
G Smith ◽  
CHL Kennard ◽  
...  

The copper(II) complex with citric acid (NH4)4 [Cu(C6H5O7)2] has been prepared, and its structure determined by X-ray diffraction, giving a residual R 0.035 for 1208 observed reflections. Crystals are monoclinic, space group P21/c with Z 2 in a cell of dimensions a 8.755(3), b 13.185(4), c 9.364(2)Ǻ, β 113.73(2)°. The complex is a centrosymmetric six-coordinate monomer which is isomorphous with ammonium zinc(II) citrate. However, the Cu-O(hydroxyl) bonds [2.341(3)Ǻ] show Jahn-Teller distortion relative to the Cu-O(carboxyl) bonds [1.969(3) and 1.977(3)Ǻ].


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