Properties of the laboratory spectra used in this work. Left panel: FWHM as a function of the temperature for the ice mixtures. The band profile narrows or broadens with increasing temperature depending on the ice sample. Right panel: FWHM plotted against the peak position. The peak centers of the CO₂:H₂O (aquamarine) and CO₂:CH₃OH (dark green) polar ices shift to longer wavelengths as the ice is heated. Similarly, the peak center of pure CO₂ ice also shifts to longer wavelengths with increasing temperature (dark red). The apolar CO₂:CO (gold and orange) ices show the opposite behavior, with peaks shifting to shorter wavelengths as a function of temperature. The blue, red, and purple squares show the FWHM and peak positions of the fitted Gaussian profiles.