NEAR-INFRARED BAND STRENGTHS OF MOLECULES DILUTED IN N₂AND H₂O ICE MIXTURES RELEVANT TO INTERSTELLAR AND PLANETARY ICES

Abstract

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, H2O 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, 1–2.5 μm) with better-known mid-infrared features (4000–400 cm−1, 2.5–25 μm) at longer wavelengths.