2013A&A...555A..85I

The ν₂ bending mode of pure CO₂ ice around 15.2µm exhibits a fine double-peak structure that offers a sensitive probe to study the physical and chemical properties of solid CO₂ in space. Current laboratory spectra do not fully resolve the CO₂ ice features. To improve the fitting of the observed CO₂ features, high-resolution solid-state infrared spectra of pure CO₂ ice are recorded in the laboratory for a series of astronomically relevant temperatures and at an unprecedented level of detail. The infrared spectra of pure CO₂ ice were recorded in the 4000 to 400cm^–1 (2.5-25µm) region at a resolution of 0.1/cm using Fourier transform infrared spectroscopy. Accurate band positions and band widths (FWHM) of pure CO₂ ice are presented for temperatures of 15, 30, 45, 60, and 75K. The focus of this spectroscopic work is on the CO₂ (ν₂) bending mode, but more accurate data are also reported for the ¹²CO₂ and ¹³CO₂ (ν₃) stretching mode, and CO₂ (ν₁+ν₃) and (2ν₂+ν₃) combination bands.