Publication Date:
2012-01-01
Description:
The single-crystal Raman spectra of the natural mineral paulmooreite Pb2As2O5 from the Långban, Filipstad district, Värmland province, Sweden, are presented for the first time. It is a monoclinic mineral containing an isolated [As2O5]4- dimer. Unpolarized single-crystal spectra of the natural and synthetic samples compare favorably with each other and are characterized by strong bands around 186 and 140 cm-1 and three medium bands at 800–700 cm-1. Band assignments were made based on band symmetry and spectral comparison between experimental band positions and those resulting from Hartree-Fock calculation of an isolated [As2O5]4- anion complex. Spectral comparison was also made with lead arsenites such as synthetic PbAs2O4 and Pb2(AsO2)3Cl and natural finnemanite to determine the contribution of the terminal and bridging O in paulmooreite. Bands at 760–733 cm-1 were assigned to terminal As-O vibrations, whereas stretches of the bridging O occur at 562 and 503 cm-1. The single-crystal spectra showed good mode separation, allowing bands to be assigned a symmetry species of Ag or Bg.
Print ISSN:
0003-004X
Electronic ISSN:
1945-3027
Topics:
Geosciences
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