FT-IR and Raman microscopic study at 293 K and 77 K of celestine, SrS0₄, from the middle triassic limestone (Muschelkalk) in Winterswijk, The Netherlands

Abstract

Abstract This paper describes the Raman and infrared spectroscopy of SrSO 4 or celestine from the Muschelkalk of Winterswijk, The Netherlands. The infrared absorption spectrum is characterised by the SO 4 2- modes V 1 at 991 cm -1 , v 3 at 1201, 1138 and 1091 cm -1 , and v 4 at 643 and 611 cm -1 . An unidentified band is observed at 1248 cm -1 . In the Raman spectrum at 293 K the V 1 mode is found at 1000 cm -1 and is split in two bands at 1001 and 1003 cm -1 upon cooling to 77 K.The v 2 mode, not observed in the infrared spectrum, is observed as a doublet at 460 and 453 cm -1 . The v 3 mode is represented by four bands in the Raman spectrum at 1187, 1158, 1110 and 1093 cm -1 and the v 4 mode as three bands at 656, 638 and 620 cm -1 . Cooling to 77 K results in a general decrease in bandwidth and a minor shift in frequencies. A decrease in intensities is observed upon cooling to 77 K due to movement of the Sr atom towards one or more of the oxygen atoms in the sulfate group.