Raman spectra of methane and methane–ethane mixtures (100, 85, and 49 mole % CH4) have been obtained as a function of pressure in the pressure range 0.1 to 15.3 MPaA (MPa absolute). For these mixtures methane υ1 (symmetric C–H stretching) band positions are given as a function of pressure; for pure methane they are in agreement with previous results. The new data on the methane υ1 band position of ethane-containing mixtures clearly depend on the kind of molecules surrounding the vibrating methane molecule. The υ1 band position decreases with increasing pressure; the stronger the dependency, the higher the content of ethane. The ethane υ1 band position in the two mixtures showed the same kind of dependency. A qualitative explanation for this behavior is attempted, relating it to changes in van der Waals-type interactions on pressure.
S. Brunsgaard Hansen, R. W. Berg, and E. H. Stenby, "Raman Spectroscopic Studies of Methane–Ethane Mixtures as a Function of Pressure," Appl. Spectrosc. 55, 745-749 (2001)