2012ApJ...759...74R

The relative abundances of ices in astrophysical environments rely on accurate laboratory measurements of physical parameters, such as band strengths (or absorption intensities), determined for the molecules of interest in relevant mixtures. In an extension of our previous study on pure-ice samples, here we focus on the near-infrared absorption features of molecules in mixtures with the dominant components of interstellar and planetary ices, H₂ O and N₂. We present experimentally measured near-infrared spectral information (peak positions, widths, and band strengths) for both H₂O- and N₂-dominated mixtures of CO (carbon monoxide), CO₂(carbon dioxide), CH₄(methane), and NH₃(ammonia). Band strengths were determined during sample deposition by correlating the growth of near-infrared features (10,000-4000/cm, 1-2.5 µm) with better-known mid-infrared features (4000-400/cm, 2.5-25 µm) at longer wavelengths.