Depolarization Ratios of Methane Raman Bands as a Function of Pressure

In this work, we measured the intensities of Q-branches of the ν₁, ν₂ and ν₃ bands in the polarized and depolarized methane Raman spectra in the pressure range of 1-60 atm. It was established that the pressure dependence of depolarization ratios of the ν₂ and ν₃ bands are negligible. In turn, the depolarization ratio of the ν₁ band increases with increasing pressure and reaches approximately 0.0045 at 60 atm. These data are more precise than previously published ones because ν₁ band intensities were determined taking into account the contribution of overlapping lines of ν₃ band. The presented data will be useful in calculating the methane polarizabilities at high pressure, as well as in calculating methane Raman spectra for measuring the natural gas composition using Raman spectroscopy.