Water formation on bare grains: When the chemistry on dust impacts interstellar gas

Cazaux, S.; Cobut, V.; Marseille, M.; Spaans, Marco; Caselli, P.

doi:10.1051/0004-6361/201014026

Cited by 89 publications

(109 citation statements)

References 53 publications

(94 reference statements)

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“…Following the usual approach in the literature (e.g. Cazaux et al 2010;Taquet et al 2013b), we assume that for each deuterated species, the binding energy is equal to that of the corresponding undeuterated species. We discuss the binding energies further in Sect.…”

Section: Chemical Modelmentioning

confidence: 99%

HD depletion in starless cores

Sipilä

Caselli

Harju

2013

A&A

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102

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Aims. We aim to investigate the abundances of light deuterium-bearing species such as HD, H 2 D + , and D 2 H + in a gas-grain chemical model that includes an extensive description of deuterium and spin-state chemistry, in physical conditions appropriate to the very centers of starless cores. Methods. We combined a gas-grain chemical model with radiative transfer calculations to simulate density and temperature structure in starless cores. The chemical model includes new reaction sets for both gas phase and grain surface chemistry, including deuterated forms of species with up to four atoms and the spin states of the light species H 2 , H + 2 , and H + 3 and their deuterated forms. Results. We find that in the dense and cold environments attributed to the centers of starless cores, HD eventually depletes from the gas phase because deuterium is efficiently incorporated into grain-surface HDO, resulting in inefficient HD production on grains for advanced core ages. HD depletion has consequences not only on the abundances of, e.g., H 2 D + and D 2 H + , whose production depends on the abundance of HD, but also on the spin state abundance ratios of the various light species, when compared with the complete depletion model where heavy elements do not influence the chemistry. Conclusions. While the eventual HD depletion leads to the disappearance of light deuterium-bearing species from the gas phase on a relatively short timescale at high density, we find that at late stages of core evolution, the abundances of H 2 D + and D 2 H + increase toward the core edge, and the distributions become extended. The HD depletion timescale increases if less oxygen is initially present in the gas phase, owing to chemical interaction between the gas and the dust preceding the starless core phase. Our results are greatly affected if H 2 is allowed to tunnel on grain surfaces, and therefore more experimental data is needed not only on tunneling but also on the O + H 2 surface reaction in particular.

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Section: Chemical Modelmentioning

confidence: 99%

HD depletion in starless cores

Sipilä

Caselli

Harju

2013

A&A

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102

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“…Tielens and Hagen (1982) proposed that interstellar water forms on grain surfaces through three reaction channels: hydrogenation of atomic, molecular oxygen and ozone. Using a Monte Carlo approach, Cuppen and Herbst (2007) and Cazaux et al (2010) showed that the contribution of the different formation channels strongly depends on the local environment in interstellar clouds. They concluded that the atomic oxygen channel is the main route in translucent and diffuse clouds, while the molecular oxygen channel, together with the ozone route, is more efficient in dense cold molecular clouds.…”

Section: Surface Formation Of Methanolmentioning

confidence: 99%

Surface formation routes of interstellar molecules: hydrogenation reactions in simple ices

Ioppolo

Cuppen

Linnartz

2011

Rend. Fis. Acc. Lincei

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It has been a long standing problem in astrochemistry to explain how molecules can form in a highly dilute environment such as the interstellar medium. In recent years it has become clear that not only ion/radical-molecule gas-phase reactions, but also solid state reactions on icy dust grains play an important role in the formation of new species. In order to investigate the underlying processes, laboratory based experiments are needed to simulate surface reactions induced by photon (UV) processing or particle (atom, cosmic ray, electron) bombardment of interstellar ice analogs. Here, the latest research performed on SURFace REaction SImulation DEvice (SURFRESIDE), one of the ultra-high vacuum setups in the Sackler Laboratory for Astrophysics in Leiden is reviewed. The focus is on hydrogenation, i.e., H-atom addition reactions in interstellar ice analogs for astronomically relevant temperatures. We discuss how molecules form when CO and O 2 containing ices are exposed to thermal hydrogen atoms under fully controlled experimental conditions. Surface formation schemes for interstellar relevant species, such as solid methanol, water, and carbon dioxide are investigated and chemical links between molecular species in space are discussed.

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“…In particular, many studies have been focused on thermal desorption Noble et al 2015) and nonthermal processes, such as photo-desorption (DeSimone et al 2013;Bertin et al 2013), sputtering (Johnson et al 2013;Cassidy et al 2013), cosmic ray (CR) desorption (Leger et al 1985;Hasegawa & Herbst 1993;Ivlev et al 2015), and chemical desorption (Cazaux et al 2010;Dulieu et al 2013;.…”

Section: Introductionmentioning

confidence: 99%

Dust as interstellar catalyst

Minissale

Dulieu

Cazaux

et al. 2015

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Context. The presence of dust in the interstellar medium has profound consequences on the chemical composition of regions where stars are forming. Recent observations show that many species formed onto dust are populating the gas phase, especially in cold environments where UV-and cosmic-ray-induced photons do not account for such processes. Aims. The aim of this paper is to understand and quantify the process that releases solid species into the gas phase, the so-called chemical desorption process, so that an explicit formula can be derived that can be included in astrochemical models. Methods. We present a collection of experimental results of more than ten reactive systems. For each reaction, different substrates such as oxidized graphite and compact amorphous water ice were used. We derived a formula for reproducing the efficiencies of the chemical desorption process that considers the equipartition of the energy of newly formed products, followed by classical bounce on the surface. In part II of this study we extend these results to astrophysical conditions. Results. The equipartition of energy correctly describes the chemical desorption process on bare surfaces. On icy surfaces, the chemical desorption process is much less efficient, and a better description of the interaction with the surface is still needed. Conclusions. We show that the mechanism that directly transforms solid species into gas phase species is efficient for many reactions.

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Water formation on bare grains: When the chemistry on dust impacts interstellar gas

Cited by 89 publications

References 53 publications

HD depletion in starless cores

HD depletion in starless cores

Surface formation routes of interstellar molecules: hydrogenation reactions in simple ices

Dust as interstellar catalyst

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