Ice Coverage of Dust Grains in Cold Astrophysical Environments

Потапов, А. В.; Jäger, Cornelia; Henning, Thomas

doi:10.1103/physrevlett.124.221103

Cited by 32 publications

(38 citation statements)

References 59 publications

(65 reference statements)

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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

A&A

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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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Section: Astrophysical Implicationsmentioning

confidence: 89%

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

Molpeceres

Zaverkin

Watanabe

et al. 2021

A&A

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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: 86%

“…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. [50] for a discussion). In addition, agglomeration of H2O molecules may result in grain surfaces presenting both wet and dry areas even for a "thick" ice mantle.…”

Section: Laboratory Astrophysicsmentioning

confidence: 99%

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

Потапов

McCoustra

2021

International Reviews in Physical Chemistry

Self Cite

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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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“…On planet Earth, through hydrogen bonding between water monomers, stable water nanoclusters, both neutral and ionized, are easily formed in molecular beams (Carlon, 1981), occur naturally in the water vapour of earth's atmosphere (Aplin and McPheat, 2005), and are produced from amorphous ice by energetic ion bombardment (Martinez, 2019). In the cosmos, therefore, a natural route to water nanocluster formation would be via the ejection from amorphous water-ice coatings of cosmic dust grains (Dulieu et al ., 2010; Potapov et al ., 2020), which are believed to be abundant in interstellar clouds because they are a product of supernovae explosions (Matsuura et al ., 2019). As a prime example, cosmic ray ionization of H 2 molecules adsorbed on amorphous ice-coated dust grains can lead to the reaction (Duley, 1996): …”

Section: Water Nanoclustersmentioning

confidence: 99%

Cosmology, astrobiology and the RNA world: just add quintessential water

Johnson

2021

International Journal of Astrobiology

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Laboratory generation of water nanoclusters from amorphous ice and strong terahertz (THz) radiation from water nanoclusters ejected from water vapour into a vacuum suggest the possibility of water nanoclusters ejected into interstellar space from abundant amorphous ice-coated cosmic dust produced by supernovae explosions. Water nanoclusters (section ‘Water nanoclusters’) offer a hypothetical scenario connecting major mysteries of our Universe: dark matter (section ‘Baryonic dark matter’), dark energy (section ‘Dark energy’), cosmology (section ‘Cosmology’), astrobiology (section ‘Astrobiology’) and the RNA world (section ‘The RNA world’) as the origin of life on Earth and habitable exoplanets. Despite their expected low density in space compared to hydrogen, their quantum-entangled diffuse Rydberg electronic states make cosmic water nanoclusters a candidate for baryonic dark matter that can also absorb, via the microscopic dynamical Casimir effect, the virtual photons of zero-point-energy vacuum fluctuations above the nanocluster cut-off vibrational frequencies, leaving only vacuum fluctuations below these frequencies to be gravitationally active, thus leading to a possible common origin of dark matter and dark energy. This picture includes novel explanations of the small cosmological constant, the coincidence of energy and matter densities, possible contributions of the red-shifted THz radiation from cosmic water nanoclusters at redshift z ≅ 10 to the cosmic microwave background (CMB) spectrum, the Hubble constant crisis, the role of water as a known coolant for rapid early star formation and ultimately, how life may have originated from RNA protocells on Earth and exoplanets and moons in the habitable zones of developed solar systems. Together, they lead to a cyclic universe cosmology – based on the proposed equivalence of cosmic water nanoclusters to a quintessence scalar field – instead of a multiverse based on cosmic inflation theory. Recent CMB birefringence measurements may support quintessence. Finally, from the quantum chemistry of water nanoclusters interacting with prebiotic organic molecules, amino acids and RNA protocells on early Earth and habitable exoplanets, this scenario is consistent with the anthropic principle that our Universe must have those properties which allow life, as we know it – based on water, to develop at the present stage of its history.

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Ice Coverage of Dust Grains in Cold Astrophysical Environments

Cited by 32 publications

References 59 publications

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

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

Cosmology, astrobiology and the RNA world: just add quintessential water

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Ice Coverage of Dust Grains in Cold Astrophysical Environments

Cited by 32 publications

References 59 publications

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

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

Cosmology, astrobiology and the RNA world: just add quintessential water

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Product

Resources

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

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