Upper panel: absorption profile of the CN stretching mode of methyl cyanide, around 2252.2 cm⁻¹ (4.440 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 CN stretching mode of CH₃CN in different ice mixtures at selected temperatures. Bottom right: relative band strengths of the CN stretching band in different ice mixtures at 15 K.