Laboratory spectra of CO2 vibrational modes in planetary ice analogs

Laboratory spectra have shown that CO2 is a powerful diagnostic tool for analyzing infrared data from remote observations, as it has been detected on icy moons in the outer Solar System as well as dust grain surfaces in the interstellar medium (ISM). IR absorption band profiles of CO2 within ice mixtures containing H2O and CH3OH change with respect to temperature and mixture ratios. In this particular study, the ν3 CO2 asymmetric stretch mode near 4.3 μm (2350 cm−1), overtone mode near 1.97 μm (5080 cm−1), and the combination bands near 2.7 μm (3700 cm−1), 2.8 μm (3600 cm−1), and 2.02 μm (4960 cm−1), are systematically observed in different mixtures with H2O and CH3OH in temperature ranges from 15 K to 150 K. Additionally, some high-temperature deposits (T > 50 K) of H2O, CH3OH, and CO2 ice mixtures were performed and it was discovered that CO2 may deposit out at higher temperatures than previously recorded. These data may then be used to interpret infrared observational data obtained from icy surfaces in the outer Solar System and beyond.