Upper panel: Absorption profile of the C–H symmetric stretch mode of methyl cyanide, around 2940.9 cm⁻¹ (3.400 µm), in pure and mixed ices. The ice spectra at different temperatures are indicated by different colors and labels. Bottom left: Peak position and FWHM of the C–H symmetric stretching mode of CH₃CN in different ice mixtures at selected temperatures. Bottom right: relative band strengths of the C–H symmetric stretch band in different ice mixtures at 15 K.