p-f and f-f transitions of U6+O5F and U5+O5F centers in LiF

Abstract

An overall analysis of the energy levels of U 6ϩ O 5 F and U 5ϩ O 5 F centers of C 4v symmetry in LiF is presented. First, the experimental energies of the fine-structure lines of seven p-f transitions of the prominent (U 6ϩ O 5 F) 5ϩ center of C 4v symmetry are determined from well resolved absorption spectra in the UV range and from polarized emission and excitation experiments in the range 18 000-40 000 cm Ϫ1 . Second, a comparison with the f-f energy levels of U 5ϩ previously observed in x or ␥ irradiated UO 5 F centers shows that the energies of the p-f transitions of U 6ϩ can be approximately accounted for by shifting the energies of the f-f transitions of U 5ϩ by ⌬ϭ19 493 cm Ϫ1 , ⌬ representing the energy difference between the center of gravity of the fine-structure levels of the first excited level and the fundamental level of the configuration 5 f 0 . Finally, an analysis of the fine-structure lines associated to the p-f transitions and a comparison with the relativistic electronic structures of configurations 5 f 0 and 5 f 1 of cubic molecules UF 6 , UF 6Ϫ , and NpF 6 are made in order to determine which p and f orbitals are associated to the observed p-f transitions of U 6ϩ .

Theoretical Investigations of Geometry, Electronic Structure and Stability of UO6: Octahedral Uranium Hexoxide and Its Isomers†

“…As a typical “early actinoid”, uranium has 6 valence-active electrons in a band of spin−orbit split 5f 5/2,7/2 , 6d 3/2,5/2 , and 7s 1/2 orbitals, which lead to common OS of +3, +4, and +6, and to less common ones of +2 and +5. Remarkable structures of U VI compounds have been found, although no experimental indications yet for higher oxidation states, see for example ref , Pyykkö et al had computationally investigated the UO 6 species already a decade ago . A spectacular aspect of their work was a potential jump of the known HOS of +8 to a new record of +12, provided one attaches the common OS of −2 to the oxygens of UO 6 .…”

Investigations on the defect structures for Mn2+ in CdSe nanocrystals and bulk materials and the criterion of occupation for Mn2+ in CdX (X = S, Se, Te) nanocrystals

“…From the optical spectral studies for Mn 2+ in selenides, 30,31 the cubic CF parameters Dq (≈À360 and À400 cm À1 ) and the covalency factors N (≈0.76 and 0.76) are obtained for Mn 2+ in CdSe nanocrystals and bulk materials. By using the Mn 2+ -Se 2À distances R (≈2.571 and 2.573 Å 24,25 ) at the core of CdSe:Mn 2+ nanocrystals and in bulk materials as well as the Slater-type selfconsistent-field wave functions, 32,33 the group overlap integrals S π , S σ , and S s and the integral W can be calculated.…”