[en] Ammonium tetrachlorouranate(III) tetrahydrate may easily be converted into uranium trichloride at a non-static high-vacuum of 10^-5 - 10^-6 Pa and temperatures ranging from 20-400⁰C. (author)

[en] A series of anhydrous uranium (+3) complex chlorides of the type M₂UCl₅ (M= NH₄⁺, K⁺, Rb⁺) has been isolated and characterized by magnetic and spectral measurements. A number of calculations of the ''free ion'' levels of the 5f³ configuration were carried out in order to determine which states are the most sensitive to changes in the energy level parameters F₂, zeta sub(5f), α, β and γ. The results of calculations are discussed with respect to the energy level assignment of uranium (+3). (author)

[en] Temperature-dependent line broadening measurements of emission and excitation transitions for two intrinsic sites U(1) and U(2) of U³⁺ ions doped in a RbY₂Cl₇ single crystals as well as of U⁴⁺ ions have been performed. Values of the electron phonon (EP) coupling parameter α-bar were determined by a fit of experimentally observed line widths to an equation containing the temperature dependent broadening term due to the Raman two-phonon process. The α-bar parameters for U³⁺ ions in RbY₂Cl₇ are larger than those determined for this ion in LaCl₃ host crystals. This is due to shorter M-Cl distances in RbY₂Cl₇ which leads to a stronger interaction of uranium with the chlorine ions and to an increase of covalency. The relatively large α-bar value determined for the ²H2_11/2 multiplet of U³⁺ in RbY₂Cl₇ may result from the proximity of opposite parity 5f²6d¹ states. The α-bar parameters obtained for the U³⁺ ions are larger than those for U⁴⁺. The latter ones are affected by a stronger crystal-field (CF), however the position of the first 5f²6d¹ or 5f¹6d¹ states, which for U³⁺ is observed at an energy of ∼15,000 cm^-1 lower than for U⁴⁺, is the dominating one among the factors influencing the EP coupling strength. The EP coupling parameters for all investigated transitions of the U³⁺ ions are larger for U(2) than for U(1), which results mainly from the larger crystal field strength observed for the U(2) site. The differences in the EP coupling strength of the U³⁺ ions in the U(1) and U(2) sites are in accordance with decay times observed for emission for both sites from the ⁴F_9/2 multiplet

[en] Uranium(3+) doped Cs₂NaYBr₆ single crystals with a 2.1 and 0.09 mol% U³⁺ concentration have been obtained by the Bridgman-Stockbarger method. The U³⁺ ions replaced the Y³⁺ ions at an octahedral site of O_h symmetry. Luminescence spectra of the crystal were recorded at 4.2 K. The emission bands observed in the visible and near infrared regions have been assigned to transitions from the lowest components of the ⁴G_7/2 and ⁴F_3/2 multiplets to the crystal-field components of the ⁴I_9/2 ground state. Absorption spectra were recorded in the 3900-35,000 cm^-1 range at 4.2 K. The analysis of these spectra enabled the assignement of 28 energy levels, which were fitted to seven parameters of an empirical Hamiltonian representing the combined atomic and crystal-field interactions, with a rms deviation of 43 cm^-1. The energies of the most prominent vibronic features have been measured and assigned to the specific vibrational modes of the UCl₆^3- moiety or to lattice modes. Above 14,000 cm^-1 vibronic transitions associated with the electric dipole allowed 5f³-5f²6d¹ transitions were observed. The unresolved zero-phonon lines are accompanied by a number of vibrational progressions combined with the even S₁(a_1g) mode

[en] The absorption spectra of uranium(+3) in 2 M HC10₄, of uranium(+3) chloro-complexes in anhydrous methyl alcohol and dimethylformamide, and of uranium(+3) thiocyanato-complexes in anhydrous methyl alcohol, were recorded in the range 4000 to 50,000 cm^-1. An intensity analysis of f-f transitions of the uranium(+3) spectra in 2 M HC10₄ and anhydrous methyl alcohol, has been made and is discussed with respect to the energy level assignment. Calculations of the 'free ion' energy levels, were carried out in order to determine which states of the configuration 5f³ are most sensitive to changes in the energy level parameters. (author)

[en] Short communication

No abstract available

[en] Uranium(III) chloro complexes of the formulas SrUCl₅ and Ba₂UCl₇ were synthesized and characterized by electronic absorption spectra, X-ray powder diffraction and magnetic susceptibility investigations. Ba₂UCl₇ crystallizes in the monoclinic system, P2₁/c, with a=7.20 A, b=15.61 A, c=10.66 A, β=91.1 and Z=4. Magnetic susceptibilities of polycrystalline samples of the compounds were measured on a SQUID magnetometer in the 1.7-300 K range. The inverse magnetic susceptibility versus temperature plots of SrUCl₅ and Ba₂UCl₇ follow the Curie-Weiss law above 90 and 105 K, respectively. The following paramagnetic constants from the Curie-Weiss law C=χ_M(T-Θ) have been obtained: C=1.653 emu.K.mol^-1, Θ=-127 K, μ_eff=2.84√(c)=3.65 B.M. (for SrUCl₅) and C=1.310 emu.K.mol^-1, Θ=-95 K, μ_eff=3.25 B.M. (for Ba₂UCl₇). Solid state electronic spectra of the compounds have been recorded in the 4000-30000 cm^-1 range and are discussed. (orig.)

[en] Pure uranium tribromide may be prepared by applying an effective non-static high vacuum of 10^-5-10^-6 hPa over the temperature range 20 to 350⁰C to NH₄UBr₄·1.5CH₃CN·6H₂O. (author)

[en] A method of preparation of two new uranium (3+) compounds of the formulas K₂UBr₅.2CH₃CN.6H₂O and Rb₂UBr₅.CH₃CN.6H₂O is given. High vacuum thermal decomposition of the complexes enabled obtaining the anhydrous pentabromouranates(III)-K₂UBr₅ and Rb₂UBr₅. The former complexes were characterized by magnetic susceptibility measurements in the 4-300 K range as well as by electronic and i.r. spectra in the 4000-24000 cm^-1 and 80-4000 cm^-1 spectral ranges, respectively