title: Raman spectroscopy of uranyl rare earth carbonate kamotoite-(Y).
abstract: Raman spectroscopy at 298 and 77K has been used to study the mineral kamotoite-(Y), a uranyl rare earth carbonate mineral of formula Y(2)(UO(2))(4)(CO(3))(3)(OH)(8).10-11H(2)O. The mineral is characterised by two Raman bands at 1130.9 and 1124.6 cm(-1) assigned to the nu(1) symmetric stretching mode of the (CO(3))(2-) units, while those at 1170.4 and 862.3 cm(-1) (77K) to the deltaU-OH bending vibrations. The assignment of the two bands at 814.7 and 809.6 cm(-1) is difficult because of the potential overlap between the symmetric stretching modes of the (UO(2))(2+) units and the nu(2) bending modes of the (CO(3))(2-) units. Only a single band is observed in the 77K spectrum at 811.6 cm(-1). One possible assignment is that the band at 814.7 cm(-1) is attributable to the nu(1) symmetric stretching mode of the (UO(2))(2+) units and the second band at 809.6 cm(-1) is due to the nu(2) bending modes of the (CO(3))(2-) units. Bands observed at 584 and 547.3 cm(-1) are attributed to water librational modes. An intense band at 417.7 cm(-1) resolved into two components at 422.0 and 416.6 cm(-1) in the 77K spectrum is assigned to an Y(2)O(2) stretching vibration. Bands at 336.3, 286.4 and 231.6 cm(-1) are assigned to the nu(2) (UO(2))(2+) bending modes. U-O bond lengths in uranyl are calculated from the wavenumbers of the uranyl symmetric stretching vibrations. The presence of symmetrically distinct uranyl and carbonate units in the crystal structure of kamotoite-(Y) is assumed. Hydrogen-bonding network related to the presence of water molecules and hydroxyls is shortly discussed.
authors.affiliation: Inorganic Materials Research Program, School of Physical and Chemical Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, Qld 4001, Australia. r.frost@qut.edu.au <r.frost@qut.edu.au>
authors.forename: Ray L
authors.initials: RL
authors.lastname: Frost
authors.forename: Matt L
authors.initials: ML
authors.lastname: Weier
authors.forename: Jirí
authors.initials: J
authors.lastname: Cejka
authors.forename: Godwin A
authors.initials: GA
authors.lastname: Ayoko
mesh_terms: D002254:Carbonates / Q000737:chemistry; D008903:Minerals / Q000737:chemistry; D013059:Spectrum Analysis, Raman; D017974:Uranium Compounds / Q000737:chemistry*; D015019:Yttrium / Q000737:chemistry*
chemical_list: D002254:Carbonates; D008903:Minerals; D017974:Uranium Compounds; D015019:Yttrium