Raman Spectroscopic Investigation of Sulfates Using Mosaic Grating Spatial Heterodyne Raman Spectrometer

Abstract

We introduce a field-widened spatial heterodyne Raman spectrometer with a mosaic grating structure to investigate the broadband Raman spectra of sulfates. The broadband static spatial heterodyne Raman spectrometer configuration employs two mosaic gratings instead of the diffraction gratings to divide the broadband Raman spectrum into two bands. It is able to record high-resolution, broadband Raman spectrum range, covering 5740 cm-1 with 3.061 cm-1 spectral resolution using a regular CCD in a single-shot measurement. Raman spectra of mineral sulfates (celestine, gypsum) are investigated. This is the first time to conduct this Raman spectroscopic experiments to investigate the sulfates using the spatial heterodyne Raman spectroscopy. The sodium, potassium and ammonium sulfates at solid state and in aqueous solutions had been detected and analyzed. The effects of metal ions (K+, Na+, NH4+, Ca2+, Sr2+) on vibration of sulfate anion SO42- were discussed. The main v1 mode can be probed by the spatial heterodyne Raman spectroscopy to determine the concentration of sulfate and unambiguous identification of different sulfate minerals, solid sulfates.

Keywords

• Spectroscopy
• spatial heterodyne spectrometer
• broadband
• high-resolution
• field widening