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- Volume 84 - Année 2015
- Actes de colloques
- Workshop d'astrochimie expérimentale
- Thermal processing of astrophysical ice analogs using the Interstellar Astrochemistry Chamber
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Thermal processing of astrophysical ice analogs using the Interstellar Astrochemistry Chamber
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Thermal processing of astrophysical ices takes place in circumstellar environments. Knowledge of this process comes from a combination of astronomical observations and laboratory simulations under astrophysically relevant conditions. For the first time we present the results of temperature programmed desorption (TPD) experiments with realistic pre-cometary ice analogs composed of up to five molecular components: H2O, CO, CO2, CH3OH, and NH3. The experiments were performed with an ultra-high vacuum chamber. Volatiles desorbing to the gas phase were monitored using a quadrupole mass spectrometer, while changes in the ice structure and composition were studied by means of infrared spectroscopy. The TPD curves of water ice containing CO, CO2, CH3OH, and NH3 present desorption peaks at temperatures near those observed in pure ice experiments, volcano desorption peaks after water ice crystallization, and co-desorption peaks with water. Desorption peaks of CH3OH and NH3 at temperatures similar to the pure ices takes place when their abundance relative to water is above — 3 % in the ice matrix. We found that CO, CO2, and NH3 also present co-desorption peaks with CH3OH, which is the only species that segregated enough to allow detection in the IR spectra. These results reproduce the heating of circumstellar ices in hot cores and can be also applied to the late thermal evolution of comets.