Depolarization Ratio of the ν1 Raman Band of Pure CH4 and Perturbed by N2 and CO2

In this work, the effect of nitrogen and carbon dioxide on the depolarization ratio of the ν₁ band of methane in the pressure range of 0.1–5 MPa is studied. A high-sensitivity single-pass Raman spectrometer was used to obtain accurate results. Moreover, we took into account the overlap of the ν₁ band by the ν₃ and ν₂ + ν₄ bands using the simulation of their spectra. The depolarization ratio of the ν₁ band in pure methane is within 0–0.001, and the effect of nitrogen and carbon dioxide on this parameter is negligible in the indicated pressure range. The obtained results are useful for correct simulation of the Raman spectrum of methane at different pressures, which is necessary to improve the accuracy of gas analysis methods using Raman spectroscopy.