Raman spectral behavior of N 2 , CO 2 , and CH 4 in N 2 –CO 2 –CH 4 gas mixtures from 22°C to 200°C and 10 to 500 bars, with application to other gas mixtures

The Raman spectral behavior of N 2 , CO 2 , and CH 4 in ternary N 2 –CO 2 –CH 4 mixtures was studied from 22°C to 200°C and 10 to 500 bars. The peak position of N 2 in all mixtures is located at lower wavenumbers compared with pure N 2 at the same pressure ( P )–temperature ( T ) ( PT ) conditions. The Fermi diad splitting in CO 2 is greater in the pure system than in the mixtures, and the Fermi diad splitting increases in the mixtures as CO 2 concentration increases at constant P and T . The peak position of CH 4 in the mixtures is shifted to higher wavenumbers compared with pure CH 4 at the same PT conditions. However, the relationship between peak position and CH 4 mole fraction is more complicated compared with the trends observed with N 2 and CO 2 . The relative order of the peak position isotherms of CH 4 and N 2 in the mixtures in pressure–peak position space mimics trends in the molar volume of the mixtures in pressure–molar volume space. Relationships between the direction of peak shift of individual components in the mixtures, the relative molar volumes of the mixtures, and the attraction and repulsion forces between molecules are developed. Additionally, the relationship between the peak position of N 2 in ternary N 2 –CO 2 –CH 4 mixtures with pressure is extended to other N 2 ‐bearing systems to assess similarities in the Raman spectral behavior of N 2 in various systems.