Fast neutron radiation on single-crystal thorium dioxide. An optical absorption spectroscopy study of the Fo Colour centre

1992 ◽  
Vol 88 (23) ◽  
pp. 3475 ◽  
Author(s):  
Trevor R. Griffiths ◽  
James Dixon
Keyword(s):  
Optical Absorption ◽  
Single Crystal ◽  
Fast Neutron ◽  
Absorption Spectroscopy ◽  
Neutron Radiation ◽  
Optical Absorption Spectroscopy ◽  
Spectroscopy Study ◽  
Colour Centre ◽  
Thorium Dioxide

H-bonding scheme in allactite: a combined single-crystal X-ray and neutron diffraction, optical absorption spectroscopy, FTIR and EPMA-WDS study

2016 ◽  
Vol 80 (5) ◽  
pp. 719-732 ◽  
Author(s):  
G. Diego Gatta ◽  
Ferdinando Bosi ◽  
Maria Teresa Fernandez Diaz ◽  
Ulf Hålenius
Keyword(s):  
Neutron Diffraction ◽  
Optical Absorption ◽  
Single Crystal ◽  
Absorption Spectroscopy ◽  
Structure Refinement ◽  
Site Occupancy ◽  
Optical Absorption Spectroscopy ◽  
Hydroxyl Groups ◽  
X Ray ◽  
Bonding Scheme

AbsatractThe crystal chemistry of allactite from Långban, Värmland (Sweden) was investigated by single-crystal X-ray and neutron diffraction, optical absorption spectroscopy, Fourier-transform infra-red spectroscopy (FTIR) and electron microprobe analysis by wavelength-dispersive spectroscopy (EPMA-WDS). The optical spectra indicate the presence of Mn in valence state 2+ only. Assuming 16 O atoms per formula unit, arsenic as As5+and the (OH) content calculated by charge balance, the resulting formula based on the EPMA-WDS data is (Mn2+6.73Ca0.13Mg0.12Zn0.02)∑7.00(As5+)2.00O16H8, very close to the ideal composition Mn7(AsO4)2(OH)8. In the unpolarized FTIR spectrum of allactite, fundamental (OH)-stretching bands are observed at 3236, 3288, 3387, 3446, 3484, 3562 and 3570 cm–1, suggesting that a number of OH environments, with different hydrogen bond strengths, occur in the structure. The neutron structure refinement shows that four independent H sites occur in allactite with full site occupancy, all as members of hydroxyl groups. The complex hydrogen-bonding scheme in the allactite structure is now well defined, with at least nine hydrogen bonds energetically favourable with mono-, bi- and trifurcated configurations.

Conformational Properties of Nickel(II) Octaethylporphyrin in Solution. 2. A Low-Temperature Optical Absorption Spectroscopy Study

1996 ◽  
Vol 100 (33) ◽  
pp. 14192-14197 ◽  
Author(s):  
Antonio Cupane ◽  
Maurizio Leone ◽  
Lorenzo Cordone ◽  
Harald Gilch ◽  
Wolfgang Dreybrodt ◽  
...  
Keyword(s):  
Low Temperature ◽  
Optical Absorption ◽  
Absorption Spectroscopy ◽  
Optical Absorption Spectroscopy ◽  
Spectroscopy Study ◽  
Conformational Properties
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