Sputtering of Ices

Johnson, R. E.; Carlson, R. W.; Cassidy, Timothy A.; Famá, M.

doi:10.1007/978-1-4614-3076-6_17

Cited by 23 publications

(23 citation statements)

References 158 publications

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“…Decades of mass spectrometry measurements of hydrogen and oxygen sputtering from irradiated ice (see reviews by Teolis et al, and Johnson et al, ) have revealed that the H 2 and O 2 yields increase with temperature (e.g., Baragiola et al, ; Boring et al, ; Orlando & Sieger, ) and decrease/increase, respectively, with irradiation dose at low dose (Petrik et al, ; Reimann et al, ; Sieger et al, ; Teolis et al, , ). The H 2 and O 2 are closely linked, as they both sputter stoichiometrically at high dose (> ~10 15 cm −2 ) in 2:1 (H 2 :O 2 ) proportions, as expected in accordance with the H 2 O ice's elemental composition (Johnson et al, ; Teolis et al, ).…”

Section: Molecular Hydrogen and Oxygenmentioning

confidence: 99%

Water Ice Radiolytic O₂, H₂, and H₂O₂ Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

et al. 2017

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O2, H2, and H2O2 radiolysis from water ice is pervasive on icy astrophysical bodies, but the lack of a self‐consistent, quantitative model of the yields of these water products versus irradiation projectile species and energy has been an obstacle to estimating the radiolytic oxidant sources to the surfaces and exospheres of these objects. A major challenge is the wide variation of O2 radiolysis yields between laboratory experiments, ranging over 4 orders of magnitude from 5 × 10−7 to 5 × 10−3 molecules/eV for different particles and energies. We revisit decades of laboratory data to solve this long‐standing puzzle, finding an inverse projectile range dependence in the O2 yields, due to preferential O2 formation from an ~30 Å thick oxygenated surface layer. Highly penetrating projectile ions and electrons with ranges ≳30 Å are therefore less efficient at producing O2 than slow/heavy ions and low‐energy electrons (≲ 400 eV) which deposit most energy near the surface. Unlike O2, the H2O2 yields from penetrating projectiles fall within a comparatively narrow range of (0.1–6) × 10−3 molecules/eV and do not depend on range, suggesting that H2O2 forms deep in the ice uniformly along the projectile track, e.g., by reactions of OH radicals. We develop an analytical model for O2, H2, and H2O2 yields from pure water ice for electrons and singly charged ions of any mass and energy and apply the model to estimate possible O2 source rates on several icy satellites. The yields are upper limits for icy bodies on which surface impurities may be present.

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Section: Molecular Hydrogen and Oxygenmentioning

confidence: 99%

Water Ice Radiolytic O₂, H₂, and H₂O₂ Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

et al. 2017

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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

A&A

185

227

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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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“…The latter is composed of the stellar winds (in planetary systems), magnetospheric ions (in the vicinity of planets), and cosmic radiation (everywhere). Such radiation has many effects on the grains; it may compact the material, erode it, induce phase transformations (to the amorphous phase or to other solid phases), and induce chemical transformations in the grain (Johnson 1990;Johnson et al 2013). By ejecting material, such irradiation events may set chemically transformed material -also including highly reactive radicalsfree by bringing it to the gas phase.…”

Section: Introductionmentioning

confidence: 99%

Irradiation of astrophysical ice grains by cosmic-ray ions: a REAX simulation study

Mainitz

Anders

Urbassek

2016

A&A

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Context. The impact of cosmic rays on ice grains delivers considerable energy, inducing chemical reactions and molecule ejection. Aims. We study the effects of cosmic ray impact on ice grains, including shock wave expansion, grain heating, molecule fragmentation, formation of chemical reaction products, sputtering and evaporation. Methods. Molecular-dynamics simulations using the REAX potential allow us to follow the processes occurring in the irradiated ice grain; the mechanical, thermal and chemical consequences are simulated. The ice grain consists of a mixture of water, carbon dioxide, methanol and ammonia. The case of 1 keV/nm energy deposition is studied as an example. Results. The ion track emits a shock wave into the ambient grain. Due to the strong heating, abundant molecule fragmentation is observed; several of the fragments either recombine or form new product molecules. Prompt sputtering from the ion track is followed by evaporation from the surface of the heated grain. We present mass spectra of the chemically transformed species in the grain and in the ejecta.

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Sputtering of Ices

Cited by 23 publications

References 158 publications

Water Ice Radiolytic O₂, H₂, and H₂O₂ Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

Water Ice Radiolytic O₂, H₂, and H₂O₂ Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

Dust as interstellar catalyst

Irradiation of astrophysical ice grains by cosmic-ray ions: a REAX simulation study

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Sputtering of Ices

Cited by 23 publications

References 158 publications

Water Ice Radiolytic O2, H2, and H2O2 Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

Water Ice Radiolytic O2, H2, and H2O2 Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

Dust as interstellar catalyst

Irradiation of astrophysical ice grains by cosmic-ray ions: a REAX simulation study

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Product

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Water Ice Radiolytic O₂, H₂, and H₂O₂ Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

Water Ice Radiolytic O₂, H₂, and H₂O₂ Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies