Analysis of the absorption and emission spectra of U4+ in α-ThBr 4

Abstract : The low temperature form α-ThBr4 has a scheelite structure I41/a in which the tetravalent uranium occupies the thorium site which is S4. Assuming that the ground state remains Γ 4 as in the β-ThBr4 form, the polarized absorption spectrum at 4.2 K shows that D2d is a good approximation. A peculiarity of this host is the exaltation of very numerous fluorescences of U4+ which permit to assign four Stark levels of the ground state 3H4 : Γ5 at 110 cm-1, Γ 1 at 473 cm-1, Γ1 at 623 cm-1 and Γ5 at 830 cm-1. 30 levels have been assigned and the crystal field parameters of U4+ (5f2) have been calculated in the D2d approximation : B20 = - 382, B40 = - 3 262, B44 = - 1734, B60 = - 851 and B64 = - 1828 cm-1. It is interesting to note that a small distortion in the scheelite structure of the α-ThBr4 compared with the zircon structure β-ThBr4 induces important changes in the crystal field parameters.
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Journal articles
Journal de Physique, 1988, 49 (8), pp.1425-1434. <10.1051/jphys:019880049080142500>


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Submitted on : Friday, January 1, 1988 - 8:00:00 AM
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E. Simoni, S. Hubert, M. Genet. Analysis of the absorption and emission spectra of U4+ in α-ThBr 4. Journal de Physique, 1988, 49 (8), pp.1425-1434. <10.1051/jphys:019880049080142500>. <jpa-00210822>

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