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.