Raman spectra of nitrogen, carbon dioxide, and hydrogen in a methane environment

Changes in the Raman spectra of N$_{2}$, H$_{2}$, and CO$_{2}$ are studied in the range of 200–3800 cm$^{-1}$ depending on the concentration of surrounding CH$_4$ molecules at a fixed medium pressure of 25 atm and temperature of 300 K. It has been found that changes in the spectral characteristics of purely rotational H$_2$ lines in a CH$_4$ medium are negligible, while the Q-branches of the $\nu_{1}$/2$\nu_{2}$ Fermi dyad in СO$_2$ become narrower and wavenumbers of its high-frequency component and $\nu_1$ band of N$_2$ decrease. In addition, under these conditions, the ratio of intensities of the CO$_2$ Fermi dyad Q-branch varies in proportion to the concentration of surrounding molecules of CH$_4$. The obtained data will be used in diagnosing the composition of natural gas using Raman spectroscopy.