Pressure broadening in Raman spectra of CH-N, CH-CO, and CH-CH gas mixtures.

Different molecular environments change the spectrum of a given gas sample involved in a mixture compared to the spectrum of a pure gas. It is necessary to account for this effect to improve the accuracy of the analysis of the natural gas composition by Raman spectroscopy. First, the change in the main components of natural gas (methane, nitrogen, carbon dioxide, and ethane) must be considered. This work is devoted to the mutual influence of CH-N, CH-CO, and CH-CH on their characteristic Raman bands in the range of 300-2500 cm. The half-width and asymmetry of the Q branches of N, CO, and CH as a function of methane concentration were obtained in the range of 1-50 bar. The averaged broadening coefficients of the rotational-vibrational lines of the ν band of CH perturbed by N, CO, and CH are measured. A high-sensitivity spectrometer with a resolution of 0.5 cm based on spontaneous Raman scattering was used to obtain reliable results. The algorithm and all the necessary parameters for simulating the effect of various molecular environments on the Raman bands of the main components of natural gas are presented.