Highly resolved infrared spectra of pure CO2 ice (15-75 K)

Context. The nu(2) bending mode of pure CO2 ice around 15.2 mu m 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. Aims. 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. Methods. The infrared spectra of pure CO2 ice were recorded in the 4000 to 400 cm 1 (2.5-25 mu m) region at a resolution of 0.1 cm (1) using Fourier transform infrared spectroscopy. Results. Accurate band positions and band widths (FWHM) of pure CO2 ice are presented for temperatures of 15, 30, 45, 60, and 75 K. The focus of this spectroscopic work is on the CO2 (nu(2)) bending mode, but more accurate data are also reported for the (CO2)-C-12 and (CO2)-C-13 (nu(3)) stretching mode, and CO2 (nu 1 + nu 3) and (2 nu 2 + nu 3) combination bands.