Raman spectrum of methane in nitrogen, carbon dioxide, hydrogen, ethane, and propane environments

Using binary CH₄ - mixtures with varied concentrations of H₂, N₂, CO₂, C₂H₆ and C₃H₈ and a fixed ambient pressure of 25bar, the influence of the environment on spectral characteristics (Raman shift, half-width, peak intensity) of Q-branches of the ν₁, ν₂, ν₃, and 2ν₄ methane Raman bands are investigated. It is found that depending on the environment these bands demonstrate different changes in their Raman shifts and half-widths. It is shown that the ratios of peak intensities I(ν₂)/I(ν₁)_, I(ν₃)/I(ν₁) and I(2ν₄)/I(ν₁) are very sensitive to the environment. The Raman shifts and half-widths of CH₄ bands are assumed to depend on the absolute concentration of molecules in the analyzed medium. The data obtained would be useful in Raman diagnostics of natural gas.