0000000000735567
AUTHOR
R. Grisenti
Short-range order around Er3+ in silica waveguides containing aluminium, titanium and hafnium
Er3+-doped silica waveguides, co-doped with aluminium, titanium, and hafnium oxides, were prepared using the sol-gel method and dip-coating processing. Here, we present a characterisation of the local environment around Er3+ ions, as determined from the Er L3-edge extended X-ray absorption fine structure (EXAFS) measurements performed at ESRF (France). The first coordination shell is composed of 5-6 oxygen atoms at distances ~2.32-2.35 A , slightly varying as a function of the modifier oxide. Er3+ nearest neighbors distance does not show a significant compositional dependence. On the contrary, outer shells analysis shows significant differences: Al2O3 doping (less than 2% mol) induces an or…
Evaluation of multiple-scattering contribution in extended X-ray absorption fine structure for MO4 and MO6 clusters
Abstract We present a theoretical ab initio evaluation of the multiple-scattering contribution in the extended X-ray absorption fine structure for MO4 and MO6 clusters with M = Mg, Ca, Mn, Zn, Se, Sr, Mo, Ag, Te, Ba, Nd, Tb, W, Au or Bi. The dependence of the multiple-scattering signal on the absorber type, the photoelectron angular momentum and the local distortion is discussed. It is shown that the multiple-scattering contribution is significant in the photoelectron wave-vector range up to 6–7 A−1 and strongly depends on both the path geometry and the atomic species involved in the scattering process.
Femtometer accuracy EXAFS measurements: Isotopic effect in the first, second and third coordination shells of germanium
The analysis of the EXAFS signals from 70Ge and 76Ge has evidenced the low-temperature effect of isotopic mass difference on the amplitude of relative atomic vibrations. This effect is reflected in the difference of the Debye-Waller factors of the first three coordination shells, and on the difference of nearest-neighbour average interatomic distances, evaluated with femtometer accuracy. The experimental results are in agreement with theoretical expectations.
Isotopic Effect In Extended X-Ray-Absorption Fine Structure of Germanium
Extended x-ray absorption fine structure has been measured on two powdered samples of 70Ge and 76Ge as a function of temperature from 20 to 300 K. The effect of isotopic mass difference on the amplitude of relative atomic vibrations is neatly evidenced by the temperature dependence of the difference of Debye-Waller factors. The isotopic effect is also detected on the difference of nearest-neighbor average ineratomic distances, thanks to a resolution better than 10 fm. (DOI: 10.1103/PhysRevLett.100.055901)