Surface Science Investigations of Icy Mantle Growth on Interstellar Dust Grains in Cooling Environments

Marchione, Demian; Rosu-Finsen, Alexander; Taj, Skandar; Lasne, J.; Abdulgalil, Ali Ghith Moussa; Thrower, J. D.; Frankland, Victoria L.; Collings, Mark P.; McCoustra, Martin R. S.

doi:10.1021/acsearthspacechem.9b00052

Cited by 12 publications

(12 citation statements)

References 152 publications

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“…Our results reinforce the recent proposition from Marchione et al [45] that, in contradiction to the popular Onion model, bare dust grain surface in cold astrophysical environments would be available for other species except water to adsorb onto. The authors base their idea on the experimentally demonstrated agglomeration of H2O molecules on the dust surface [46] that may result in grain surfaces presenting both wet (H2O presents as agglomerates) and dry (absence of H2O) areas.…”

Section: Discussionsupporting

confidence: 90%

Ice Coverage of Dust Grains in Cold Astrophysical Environments

2020

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Surface processes on cosmic solids in cold astrophysical environments lead to gas phase depletion and molecular complexity. Most astrophysical models assume that the molecular ice forms a thick multilayer substrate, not interacting with the dust surface. In contrast, we present experimental results demonstrating the importance of the surface for porous grains. We show that cosmic dust grains may be covered by a few monolayers of ice only. This implies that the role of dust surface structure, composition, and reactivity in models describing surface processes in cold interstellar, protostellar, and protoplanetary environments has to be reevaluated.

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Section: Discussionsupporting

confidence: 90%

Ice Coverage of Dust Grains in Cold Astrophysical Environments

2020

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“…A recent study of UV irradiation of H 2 /CO codeposited mixtures showed rich chemistry for this system owing to the interaction of an electronically excited CO molecule and the H 2 molecule (Chuang et al 2018). Moreover, very recent results are inverting the trend of considering several onion-like models of cold ices (Marchione et al 2019;Potapov et al 2020). This new set of experiments shows that small icy domains (clusters or islands) are deposited on top of the refractory phase with voids in between.…”

Section: Astrophysical Implicationsmentioning

confidence: 89%

Binding energies and sticking coefficients of H₂ on crystalline and amorphous CO ice

Molpeceres

Zaverkin

Watanabe

et al. 2021

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Context. Molecular hydrogen (H2) is the most abundant interstellar molecule and plays an important role in the chemistry and physics of the interstellar medium. The interaction of H2 with interstellar ices is relevant for several processes (e.g., nuclear spin conversion and chemical reactions on the surface of the ice). To model surface processes, quantities such as binding energies and sticking coefficients are required. Aims. We provide sticking coefficients and binding energies for the H2/CO system. These data are absent in the literature so far and could help modelers and experimentalists to draw conclusions on the H2/CO interaction in cold molecular clouds. Methods. Ab initio molecular dynamics simulations, in combination with neural network potentials, were employed in our simulations. Atomistic neural networks were trained against density functional theory calculations on model systems. We sampled a wide range of H2 internal energies and three surface temperatures. Results. Our results show that the binding energy for the H2/CO system is low on average, − 157 K for amorphous CO and −266 K for crystalline CO. This carries several implications for the rest of the work. H2 binding to crystalline CO is stronger by 109 K than to amorphous CO, while amorphous CO shows a wider H2 binding energy distribution. Sticking coefficients are never unity and vary strongly with surface temperature, but less so with ice phase, with values between 0.95 and 0.17. With the values of this study, between 17 and 25% of a beam of H2 molecules at room temperature would stick to the surface, depending on the temperature of the surface and the ice phase. Residence times vary by several orders of magnitude between crystalline and amorphous CO, with the latter showing residence times on the order of seconds at 5 K. H2 may diffuse before desorption in amorphous ices, which might help to accommodate it in deeper binding sites. Conclusions. Based on our results, a significant fraction of H2 molecules will stick on CO ice under experimental conditions, even more so under the harsh conditions of prestellar cores. However, with the low H2–CO binding energies, residence times of H2 on CO ice before desorption are too short to consider a significant population of H2 molecules on pure CO ices. Diffusion is possible in a time window before desorption, which might help accommodate H2 on deeper binding sites, which would increase residence times on the surface.

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“…However, recent laboratory studies have shown that the bare dust material would be available for the surface processes in cold astrophysical environments. The experiments on the agglomeration of H2O molecules on the dust surface by Rosu-Finsen et al and Marchione et al [47,48] and on the thermal desorption of H2O and CO ices mixed with dust grains by Potapov et al [49,50] clearly demonstrate this finding. Cosmic dust grains may be covered by a submonolayer or few layer quantities of ice due to their fractal nature, high porosity and corresponding large surface area (see ref.…”

Section: Laboratory Astrophysicsmentioning

confidence: 85%

“…Thereafter "thick" ice mantles are generally assumed and atom addition chemistry occurs on the icy mantle surface. However, if the bare dust material in astrophysical environments is available for the surface processes as proposed in [48,50], bare grain surface processes will occur on the full grain lifecycle from the interstellar, protostellar, and protoplanetary phases.…”

Section: Mennella Et Al Irradiated H2o Ices On Hydrogenated Amorphous...mentioning

confidence: 99%

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Physics and chemistry on the surface of cosmic dust grains: a laboratory view

Потапов

McCoustra

2021

International Reviews in Physical Chemistry

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Dust grains play a central role in the physics and chemistry of cosmic environments. They influence the optical and thermal properties of the medium due to their interaction with stellar radiation; provide surfaces for the chemical reactions that are responsible for the synthesis of a significant fraction of key astronomical molecules; and they are building blocks of pebbles, comets, asteroids, planetesimals, and planets. In this paper, we review experimental studies of physical and chemical processes, such as adsorption, desorption, diffusion, and reactions forming molecules, on the surface of reliable cosmic dust grain analogues as related to processes in diffuse, translucent, and dense interstellar clouds, protostellar envelopes, planetforming disks, and planetary atmospheres. The information that such experiments reveal should be flexible enough to be used in many different environments. In addition, we provide a forward look discussing new ideas, experimental approaches, and research directions.

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Surface Science Investigations of Icy Mantle Growth on Interstellar Dust Grains in Cooling Environments

Cited by 12 publications

References 152 publications

Ice Coverage of Dust Grains in Cold Astrophysical Environments

Ice Coverage of Dust Grains in Cold Astrophysical Environments

Binding energies and sticking coefficients of H₂ on crystalline and amorphous CO ice

Physics and chemistry on the surface of cosmic dust grains: a laboratory view

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Surface Science Investigations of Icy Mantle Growth on Interstellar Dust Grains in Cooling Environments

Cited by 12 publications

References 152 publications

Ice Coverage of Dust Grains in Cold Astrophysical Environments

Ice Coverage of Dust Grains in Cold Astrophysical Environments

Binding energies and sticking coefficients of H2 on crystalline and amorphous CO ice

Physics and chemistry on the surface of cosmic dust grains: a laboratory view

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Product

Resources

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Binding energies and sticking coefficients of H₂ on crystalline and amorphous CO ice