Depolarization Ratios of Methane Raman Bands as a Function of Pressure

In this work, we measured the intensities of Q-branches of the ν(1), ν(2) and ν(3) 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 ν(2) and ν(3) bands are negligible. In turn, the depolarization ratio of the ν(1) band increases with increasing pressure and reaches approximately 0.0045 at 60 atm. These data are more precise than previously published ones because ν(1) band intensities were determined taking into account the contribution of overlapping lines of ν(3) 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.