Raman spectroscopic study of the uranyl selenite mineral marthozite Cu[(UO2)3(SeO3)2O2]·8H2O

The mineral marthozite, a uranyl selenite, has been characterised by Raman spectroscopy at 298 K. The bands at 812 and 797 cm⁻¹ were assigned to the symmetric stretching modes of the (UO₂)²⁺ and (SeO₃)²⁻ units, respectively. These values gave the calculated U O bond lengths in uranyl of 1.799 and/or 1.814 Å. Average U O bond length in uranyl is 1.795 Å, inferred from the X‐ray single crystal structure analysis of marthozite by Cooper and Hawthorne. The broad band at 869 cm⁻¹ was assigned to the ν₃ antisymmetric stretching mode of the (UO₂)²⁺ (calculated U O bond length 1.808 Å). The band at 739 cm⁻¹ was attributed to the ν₃ antisymmetric stretching vibration of the (SeO₃)²⁻ units. The ν₄ and the ν₂ vibrational modes of the (SeO₃)²⁻ units were observed at 424 and 473 cm⁻¹. Bands observed at 257, and 199 and 139 cm⁻¹ were assigned to OUO bending vibrations and lattice vibrations, respectively. O H···O hydrogen bond lengths were inferred using Libowiztky's empirical relation. The infrared spectrum of marthozite was studied for complementation. Copyright © 2008 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the selenite mineral: ahlfeldite,NiSeO3·2H2O

Raman spectroscopy has been used to study the selenite mineral ahlfeldite. A comparison is made with the Raman spectra of chalcomenite, cobaltomenite and clinochalcomenite. Selenite minerals are characterised by the position of the symmetric stretching mode which is observed at higher wavenumbers than the anti‐symmetric stretching mode. The selenite ion has C_3v symmetry and four modes, 2A₁ and 2E. These modes are observed at 813, 472 cm⁻¹ (A₁) and 685, 710, 727 and 367 and 396 cm⁻¹ (E). Bands assigned to the water stretching vibrations are observed for ahlfeldite at 3385 cm⁻¹, for chalcomenite at 2953, 3184 and 3506 cm⁻¹ and for clinochalcomenite at 2909, 3193 and 3507 cm⁻¹. A comparison of the Raman spectra of chalcomenite, clinochalcomenite and cobaltomenite is made. The position of these bands enabled hydrogen bond distances in the selenite structure to be estimated. Hydrogen bond distances for ahlfeldite, chalcomenite and clinochalcomenite were determined to be similar. Copyright © 2008 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the selenite minerals—chalcomenite CuSeO3·2H2O,clinochalcomenite and cobaltomenite

Raman spectroscopy has been used to study the dimorphous selenite minerals chalcomenite, cobaltomenite and clinochalcomenite. Selenite minerals are characterised by the position of the symmetric stretching mode that is observed at higher wavenumbers than the anti‐symmetric stretching mode. The selenite ion has C_3v symmetry and four modes, 2A₁ and 2E. These modes are observed at 813, 472 cm⁻¹ (A₁) and 685, 710, 727 and 367 and 396 cm⁻¹ (E). Bands assigned to the water stretching vibrations are observed for chalcomenite at 2953, 3184 and 3506 cm⁻¹ and for clinochalcomenite at 2909, 3193 and 3507 cm⁻¹. A comparison of the Raman spectra of chalcomenite, clinochalcomenite and cobaltomenite is made. The position of these bands enabled hydrogen bond distances in the selenite structure to be estimated. Hydrogen bond distances for chalcomenite and clinochalmenite were determined to be similar. Copyright © 2008 John Wiley & Sons, Ltd.