Diffusion and Clustering of Carbon Dioxide on non-porous Amorphous Solid Water

Abstract

Observations by ISO and Spitzer towards young stellar objects (YSOs) showed that CO${}_2$ segregates in the icy mantles covering dust grains. Thermal processing of ice mixture was proposed as responsible for the segregation. Although several laboratory studied thermally induced segregation, a satisfying quantification is still missing. We propose that the diffusion of CO${}_2$ along pores inside water ice is the key to quantify segregation. We combined Temperature Programmed Desorption (TPD) and Reflection Absorption InfraRed Spectroscopy (RAIRS) to study how CO${}_2$ molecules interact on a non-porous amorphous solid water (np-ASW) surface. We found that CO${}_2$ diffuses significantly on a np-ASW surface above 65~K and clusters are formed at well below one monolayer. A simple rate equation simulation finds that the diffusion energy barrier of CO${}_2$ on np-ASW is 2150$\pm$50 K, assuming a diffusion pre-exponential factor of 10${}^{12}$ s${}^{-1}$. This energy should also apply to the diffusion of CO${}_2$ on wall of pores. The binding energy of CO${}_2$ from CO${}_2$ clusters and CO${}_2$ from H${}_2$O ice have been found to be $2415\pm 20$ and $2250\pm 20$~K, respectively, assuming the same prefactor for desorption. CO${}_2$-CO${}_2$ interaction is stronger than CO${}_2$-H${}_2$O interaction, in agreement with the experimental finding that CO${}_2$ does not wet np-ASW surface. For comparison, we carried out similar experiments with CO on np-ASW, and found that the CO-CO interaction is always weaker than CO-H${}_2$O. As a result, CO wets np-ASW surface. This study should be of help to uncover the thermal history of CO${}_2$ on the icy mantles of dust grains.

arXiv comment8 pages, 11 figures, submitted to ApJ

References in corpus (10)

• Observations of the Icy Universe
• The c2d Spitzer spectroscopic survey of ices around low-mass young stellar objects II: CO2
• A 3-5 micron VLT spectroscopic survey of embedded young low mass stars I: Structure of the CO ice
• Thermal desorption characteristics of CO, O2 and CO2 on non-porous water, crystalline water and silicate surfaces at sub-monolayer and multilayer coverages
• Quantification of segregation dynamics in ice mixtures
• Binding Energy of Molecules on Water Ice: Laboratory Measurements and Modeling
• CO diffusion into amorphous H2O ices
• Sticking of molecules on non-porous amorphous water ice
• The Nature of Carbon Dioxide Bearing Ices in Quiescent Molecular Clouds
• Interactions of adsorbed CO${}_2$ on water ice at low temperatures

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• Mid-IR and VUV Spectroscopic Characterisation of Thermally Processed and Electron Irradiated CO2 Astrophysical Ice Analogues
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• Spectroscopic measurements of CH${}_3$OH in layered and mixed interstellar ice analogues
• The formation of CO${}_2$ through consumption of gas-phase CO on vacuum-UV irradiated water ice
• Molecular Mobility of Extraterrestrial Ices: Surface Diffusion in Astrochemistry and Planetary Science
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• Ammonia, carbon dioxide and the non-detection of the 2152 cm${}^{-1}$ CO band
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