Raman Spectroscopic Studies of Methane—Ethane Mixtures as a Function of Pressure

Abstract

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 MPa_A (MPa absolute). For these mixtures methane v₁ (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 v₁ band position of ethane-containing mixtures clearly depend on the kind of molecules surrounding the vibrating methane molecule. The v₁ band position decreases with increasing pressure; the stronger the dependency, the higher the content of ethane. The ethane v₁ 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.