(a) Infrared band profile of the CH₃ antisymmetric deformation mode of CH₃NH₂ (the peaks around 1479 cm⁻¹ and 1455 cm⁻¹) and the CH₃ symmetric deformation mode (around 1420 cm⁻¹), in different ices at different temperatures, from left to right: pure CH₃NH₂, CH₃NH₂:H₂O (1:10), CH₃NH₂:CH₄ (1:10), and CH₃NH₂:NH₃ (1:10). (b) Left panel: peak position vs. FWHM for the CH₃ symmetric deformation band in the ice mixtures displayed in a. Different mixtures are indicated by different colors, and the different temperatures are marked in the graph. Right panel: relative band strength of the CH₃ symmetric deformation band (1420 cm⁻¹) in different ice mixtures at 15 K. Panels c and d: same as b for the CH₃ antisymmetric deformation modes, ν₅ and ν₁₂, at 1455 and 1478.6 cm⁻¹, respectively.