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

Jun Qiu,Xiangdong Qi,Xiaotian Li

doi:10.1109/jphot.2019.2939222

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 + , Ca 2+ , Sr 2+ ) on vibration of sulfate anion SO4 2- 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.

Highlights

A tiny portion of photons are scattered with a known wavelength and polarization after a sample is irradiated by a laser beam
The proposed broadband static setup is based on using mosaic grating to create multiple narrow-band Raman spectra and combining the spatial heterodyne Raman spectroscopy (SHRS) and mosaic gratings to operation of the spectrometer at a broadband spectral range with a high resolution in a single-shot measurement
We calculated the properties of Mosaic Grating SHRS (MGSHRS), including the bandpass and spectral resolution

Summary

Introduction

A tiny portion of photons are scattered with a known wavelength and polarization after a sample is irradiated by a laser beam. In this process, the inelastic scattered photon is shifted to a different wavelength of the incident light, which either the energy (Stokes) is less than that of the incident photon or the energy (Anti-Stokes) higher than that of the incident photon. The phenomena of inelastic scattering light, which is known as the Raman effect [1]. Raman spectroscopy has been gaining popularity as a progressive method and technique for acquiring information about molecular vibrations due to requiring no sample preparation, providing significant cost saving, being nondestructive, and facilitating the direct analysis [2], [3].

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Results

Conclusion