A matrix isolation FTIR investigation of laser-ablated uranium oxide in argon and nitrogen matrices

Abstract

Uranium oxide was laser-ablated using the second harmonic of a Nd : YAG laser, and the products studied after trapping them in Ar and Nz matrices. The species obtained in the Ar matrix were UO, UO2 and UO3, which represent the primary products of laser ablation. Charge transfer complexes, (UO~) (O]) and (UO 2+) (022-) were also observed. In the N 2 matrix, in addition to the primary ablation products, reaction products with nitrogen were also observed; the prominent among them being UN2 and NUO, together with their complexes with N2. Charge transfer complexes were also seen in these experiments. Features due to NO, N3 and N] were identified, which clearly point to the role of nitrogen in these reactions•

Infrared Spectra and Electronic Structure Calculations for NN Complexes with U, UN, and NUN in Solid Argon, Neon, and Nitrogen

“…These samples had minimum UO and UO 2 contaminants. 15,32 The strong U 14 N 2 and U 15 N 2 bands at 1050.9 and 1019.4 cm −1 in solid argon exhibit an observed (anharmonic) 14 N/ 15 N frequency ratio of 1.03090, which is slightly lower than the calculated harmonic ratio 1.03117 (see the bold frequencies in Table 4). These strong absorptions are produced upon direct insertion of laser-excited U atoms into dinitrogen (eq 1), which is also initiated by full mercury arc (>220 nm) irradiation.…”

“…Diagnostic spectra from the 0.1% 14,15 N 2 reaction are presented in Figure 3. The strong antisymmetric stretching and weak symmetric stretching absorptions for 14 NU 15 N are noted at 1040.7 and 987.2 cm −1 , which reaffirm that this molecule contains two equivalent N atoms.…”

“…15 The 984 cm −1 band agrees with our earlier assignment to NUO, 13 and the five bands at 974, 964, 956, 948, and 940 cm −1 , which lead to the 938 cm −1 band for NUO in solid nitrogen, are appropriate for the five NUO(NN) 1,2,3,4,5 complexes following our above assignments to the five NUN(NN) 1,2,3,4,5 complexes.…”

“…Imido (UNX) and N−U−N molecular linkages have been prepared, 1−4 and evidence for the formation of a transient terminal uranium nitride complex following the photolysis of a uranium azide in toluene solution has been presented. 5 The synthesis and structure of bulk uranium nitride complexes is a very important topic: ligand-stabilized U(V) and U(VI) complexes have recently been prepared, and terminal UN bond of lengths 1.825 (15) and 1.799 (7) Å have been measured. 6,7 In addition, thermally stable uranium dinitrogen complexes are of interest for a possible role in nitrogen fixation.…”

“…figures showing matrix infrared spectra using 10% 14 N 2 and 8% 15 N 2 in argon, using pure nitrogen, and using 0.05 and 0.2%15 N 2 in neon; additional NU(NN) x and U(NN) 7 calculated frequencies; a figure showing corresponding complementary W and Th nitride species; and Cartesian coordinates for the title molecules. This material is available free of charge via the Internet at http://pubs.acs.org.…”