Pressure dependence of peak positions, half widths, and peak intensities of methane Raman bands (2, 24, 1, 3, and 22)

Results of investigation of changing peak positions, half widths, and peak intensities of Q-branches of the (2), 2(4), (1), (3), and 2(2) methane Raman bands are presented at pressures in the range 1-55bar and a temperature of 298K. The peak position of the (2) band remains practically unchanged, and peak positions of all other bands, by analogy with the (1) band, are shifted toward lower wavenumbers with pressure increase. It is demonstrated that the peak intensity ratio of any pair of the previously enumerated bands (except the pair of 2(4) and 2(2)) is sensitive to pressure changes. When pressure increases, the decreased peak intensities of Q-branches of depolarized (2) and (3) bands are caused by broadening of their rotational-vibrational lines, and the increased peak intensities of Q-branches of the 2(4) and 2(2) bands are most likely caused by their increased interaction with the (1) and (3) bands. A set of data obtained will be useful for the Raman analysis of natural gas and can also be used for determination of the pressure of methane-containing media. Copyright (c) 2017 John Wiley & Sons, Ltd.