12037-15-9Relevant articles and documents
Infrared spectra and quantum chemical calculations of the uranium carbide molecules UC and CUC with triple bonds
Wang, Xuefeng,Andrews, Lester,Malmqvist, Per-Ake,Roos, Bjoern O.,Goncalves, Antonio P.,Pereira, Claudia C. L.,Marcalo, Joaquim,Godart, Claude,Villeroy, Benjamin
, p. 8484 - 8488 (2010/08/05)
Laser evaporation of carbon-rich uranium/carbon alloys followed by atom reactions in a solid argon matrix and trapping at 8 K gives weak infrared absorptions for CUO at 852 and 804 cm-1. A new band at 827 cm -1 becomes a doublet with mixed carbon 12 and 13 isotopes and exhibits the 1.0381 isotopic frequency ratio, which is appropriate for the UC diatomic molecule, and another new band at 891 cm-1 gives a three-band mixed isotopic spectrum with the 1.0366 isotopic frequency ratio, which is characteristic of the linear CUC molecule. CASPT2 calculations with dynamical correlation find the C≡U≡C ground state as linear 3∑u+ with 1.840 A bond length and molecular orbital occupancies for an effective bond order of 2.83. Similar calculations with spin-orbit coupling show that the U≡C diatomic molecule has a quintet (λ = 5, δ = 3) ground state, a similar 1.855 A bond length, and a fully developed triple bond of 2.82 effective bond order.
Photoemission study of UNxOy and UCxO y in thin films
Eckle,Gouder
, p. 261 - 264 (2008/10/09)
Thin films of UNxOy and UCxOy have been prepared by reactive sputtering of U in an Ar atmosphere containing O2 and N2 admixtures, and of U and C in an Ar/O 2 atmosphere. The C content of the films was controlled by the carbon target voltage, and N and O contents were adjusted by the respective partial pressures of O2 and N2. Surface composition and electronic structure were studied by X-ray and ultra-violet photoemission spectroscopies (XPS and UPS, respectively). In most cases, the films were mixtures of the binary carbides (UC and UC2) or nitrides (UN and U2N 3), UO2 and U metal. The high reactivity of oxygen, compared to C and N2 was demonstrated. At low oxygen pressure, indications for formation of ternary uranium oxycarbides (UCxO 1-x) or oxynitrides (UNxO1-x) were obtained. These ternaries are solid solutions of UO and UC or UN (compounds containing a second constituent which fits into and is distributed in the lattice of the host compound). The metallic nature of uranium oxycarbides and oxynitrides (at low oxygen content) and the itinerant character of their 5f electrons were demonstrated.
Noble gas - Actinide complexes of the CUO molecule with multiple Ar, Kr, and Xe atoms in noble-gas matrices
Andrews, Lester,Liang, Binyong,Li, Jun,Bursten, Bruce E.
, p. 3126 - 3139 (2007/10/03)
Laser-ablated U atoms react with CO in excess argon to produce CUO, which is trapped in a triplet state in solid argon at 7 K, based on agreement between observed and relativistic density functional theory (DFT) calculated isotopic frequencies 12C16C, 13C16O, 12C18O). This observation contrasts a recent neon matrix investigation, which trapped CUO in a linear singlet state calculated to be about 1 kcal/mol lower in energy. Experiments with krypton and xenon give results analogous to those with argon. Similar work with dilute Kr and Xe in argon finds small frequency shifts in new four-band progressions for CUO in the same triplet states trapped in solid argon and provides evidence for four distinct CUO(Ar)4-n(Ng)n (Ng = Kr, Xe, n = 1, 2, 3, 4) complexes for each Ng. DFT calculations show that successively higher Ng complexes are responsible for the observed frequency progressions. This work provides the first evidence for noble gas - actinide complexes, and the first example of neutral complexes with four noble gas atoms bonded to one metal center.
Reactions of pulsed-laser evaporated uranium atoms with molecular oxygen: Infrared spectra of UO, UO2, UO3, UO2+, UO22+, and UO3-O2 in solid argon
Hunt, Rodney D.,Andrews, Lester
, p. 3690 - 3696 (2007/10/02)
Uranium atoms from the Nd:YAG laser ablation of a uranium target were codeposited with molecular oxygen and excess argon at 12 K.Infrared spectra following the U + O2 reaction revealed a wide range of reaction products.The 776.0 cm-1 band due to UO2 was the strongest product absorption, strong UO3 bands were observed at 852.5 and 745.5 cm-1, and a weak UO absorption appeared at 819.8 cm-1.These product absorptions are in agreemet with earlier work, which evaporated UO2 from a tungsten Knudsen cell at 2000 deg C.The 16O2/18O2 reaction gave only U 16O2 and U 18O2, which verified an insertion mechanism.New product absorptions were observed at 952.3, 892.3, and 842.4 cm-1.The 842.4 cm-1 absorption due to the UO3-O2 complex and the 892.3 cm-1 band assigned to the charge-transfer complex (UO2+)(O2-) grew markedly at the expense of the other uranium oxides during annealing the matrix to allow diffusion and reaction of O2.With 25percent 16O2, 50percent 16O18O, and 25percent 18O2 samples, the 952.3 cm-1 and became a sharp triplet at 952.3, 936.5, and 904.5 cm-1 and exhibited an isotopic ratio appropriate for a linear OUO species.Agreement of this bond with uranyl ion spectra suggests assignment to a (UO22+) complex.Mechanisms of formation of charged species are discussed.
Quenching of excited uranyl ion during its photochemical reduction by triphenylphosphine: Part III
Sidhu, M S,Chahat, Paramjit,Singh, R J
, p. 517 - 520 (2007/10/02)
Relative rates of bimolecular quenching of excited uranyl ion by some mono and disubstituted benzene derivatives have been measured during its photochemical reduction with triphenylphosphine.For the related compounds in a series it has been found that substitutent groups enriching the aromatic ?-electron could due to resonance stabilization, show an enhanced photophysical quenching action.The substituents decreasing the ?-electron could and delocalization of positive charge over the benzene ring decrease the quenching action.
Matrix Infrared Spectra of the Products of Uranium-Atom Reactions with Carbon Monoxide and Carbon Dioxide
Tague, Thomas J.,Andrews, Lester,Hunt, Rodney D.
, p. 10920 - 10924 (2007/10/02)
Uranium atoms from pulsed Nd:YAG laser ablation of a uranium metal target were codeposited with carbon monoxide and carbon dioxide in excess argon at 10 K.Infrared spectra following the U + CO reaction revealed strong new absorption bands at 804.4 and 852.6 cm-1, which are assigned to a CUO product on the basis of isotopic shifts, FG matrix calculations, and ab initio pseudopotential calculations.An absorption at 2027.5 cm-1 is attributed to the asymmetric secondary reaction product CU(O)CO.In both the U + CO and U + CO2 reactions, bands at 870.9 and 1963.8 cm-1 were observed and assigned to the association product of UO2 and CO.Lastly, in the U + CO2 experiments, new absorption band pairs were observed at 804.4 and 1799.6 cm-1 and at 801.5 and 2011.7 cm -1.The former pair was almost destroyed on annealing and is assigned to the OUCO insertion product.The latter pair is attributed to an OCU(O)CO species.The direct reactions of U atoms with CO and CO2 requires an activation energy, which is provided by hyperthermal U atoms from pulsed laser evaporation.
Vibrational structure of the low-lying electronic states of the UO molecule
Kaledin, L. A.,Kulikov, A. N.,Gurvich, L. V.
, p. 439 - 440 (2007/10/02)
The laser fluorescence spectra of the isotropically substituted U16O and U18O molecules have been obtained.The energies, the symmetry (Ω) the rotational constants, and the vibrational quanta of a group of low-lying electronic states have been determined.Perturbations in the vibrational structure of the electronic ground state and first excited state have been detected.
