Raman spectra of $n$-butane, isobutane, $n$-pentane, and isopentane in a methane environment

We have studied the particular features of the Raman spectra of gaseous $n$-butane, isobutane, $n$-pentane, and isopentane in a methane medium at a pressure of 25 atm. It has been found that, under these conditions, changes in the conformational equilibria of these molecules are negligible, and most significant changes in the spectra are observed in the range of 2850–3000 cm$^{-1}$, in which bands corresponding to the stretching vibrations of CH$_2$ and CH$_3$ groups shift to lower frequencies. The data obtained will be usefull in determining the composition of natural gas using Raman spectroscopy.