Surface abundance change in vacuum ultraviolet photodissociation of CO2 and H2O mixture ices

Kinugawa, Takashi; Yabushita, Akihiro; Kawasaki, Masahiro; Hama, Tetsuya; Watanabe, Naoki

doi:10.1039/c1cp20595a

Cited by 3 publications

(1 citation statement)

References 40 publications

(86 reference statements)

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“…The photolysis of H 2 O:CO 2 ice mixtures provides additional radical precursors via the following pathways (Slanger & Black 1978;Kinugawa et al 2011):…”

Section: Discussionmentioning

confidence: 99%

Quantification of O₂ formation during UV photolysis of water ice: H₂O and H₂O:CO₂ ices

Bulak

Paardekooper

Fedoseev

et al. 2022

A&A

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Context. The Rosetta and Giotto missions investigated the composition of the cometary comae of 67P/Churyumov-Gerasimenko and 1P/Halley, respectively. In both cases, a surprisingly large amount of molecular oxygen (O 2 ) was detected and was well correlated with the observed abundances of H 2 O. Laboratory experiments simulating chemical processing for various astronomical environments already showed that formation of solid state O 2 is linked to water. However, a quantitative study of O 2 formation upon UV photolysis of pure H 2 O and H 2 O dominated interstellar ice analogues is still missing. Aims. The goal of this work is to investigate whether the UV irradiation of H 2 O-rich ice produced at the earliest stages of star formation is efficient enough to explain the observed abundance of cometary O 2 . Methods. The photochemistry of pure H 16 2 O (H 18 2 O) as well as mixed H 2 O:CO 2 (ratio of 100:11, 100:22, 100:44) and H 2 O:CO 2 :O 2 (100:22:2) ices was quantified during UV photolysis. Laser desorption post-ionisation time of flight mass spectrometry (LDPI TOF MS) was used to probe molecular abundances in the ice as a function of UV fluence. Results. Upon UV photolysis of pure amorphous H 2 O ice, deposited at 20 K, formation of O 2 and H 2 O 2 is observed at abundances of, respectively, (0.9 ± 0.2)% (O 2 /H 2 O) and (1.3 ± 0.3)% (H 2 O 2 /H 2 O). To the best of our knowledge, this is the first quantitative characterisation of the kinetics of this process. During the UV photolysis of mixed H 2 O:CO 2 ices, the formation of the relative amount of O 2 compared to H 2 O increases to a level of (1.6 ± 0.4)% (for H 2 O:CO 2 ratio of 100:22), while the (H 2 O 2 /H 2 O) yield remains similar to experiments with pure water. In an ice enriched with O 2 (2%), the O 2 level increases up to 7% with regard to H 2 O, at low UV fluence, which is higher than expected on the basis of the enrichment alone. The resulting O 2 /H 2 O values derived for the H 2 O and H 2 O:CO 2 ices may account for a (substantial) part of the high oxygen amounts found in the comae of 67P and 1P.

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“…The photolysis of H 2 O:CO 2 ice mixtures provides additional radical precursors via the following pathways (Slanger & Black 1978;Kinugawa et al 2011):…”

Section: Discussionmentioning

confidence: 99%

Quantification of O₂ formation during UV photolysis of water ice: H₂O and H₂O:CO₂ ices

Bulak

Paardekooper

Fedoseev

et al. 2022

A&A

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Division Xii / Commission 14 / Working Group Solids and Their Surfaces

Vidali¹

2008

Proc. IAU

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In the last decade there has been a tremendous increase of interest in studying processes occurring on IS dust. In part this is due to the availability of ground-based and space-borne high quality instruments which have been used to detect molecules in diverse astrophysical environments, from protoplanetary disks to hot cores and dense clouds. It has also been recognized that IS dust has an important role in the formation of molecules, from molecular hydrogen to methanol. Therefore, it is necessary not to study only properties of dust, but also understand how atoms and molecules interact with and on dust.

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Wavelength resolved UV photodesorption and photochemistry of CO₂ice

et al. 2014

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Over the last four years we have illustrated the potential of a novel wavelength-dependent approach in determining molecular processes at work in the photodesorption of interstellar ice analogs. This method, utilizing the unique beam characteristics of the vacuum UV beamline DESIRS at the French synchrotron facility SOLEIL has revealed an efficient indirect desorption mechanism that scales with the electronic excitations in molecular solids. This process, known as DIET--desorption induced by electronic transition--occurs efficiently in ices composed of very volatile species (CO, N2), for which photochemical processes can be neglected. In the present study, we investigate the photodesorption energy dependence of pure and pre-irradiated CO2 ices at 10-40 K and between 7 and 14 eV. The photodesorption from pure CO2 is limited to photon energies above 10.5 eV and is clearly initiated by CO2 excitation and by the contribution of dissociative and recombination channels. The photodesorption from "pre-irradiated" ices is shown to present an efficient additional desorption pathway below 10 eV, dominating the desorption depending on the UV-processing history of the ice film. This effect is identified as an indirect DIET process mediated by photoproduced CO, observed for the first time in the case of less volatile species. The results presented here pinpoint the importance of the interconnection between photodesorption and photochemical processes in interstellar ices driven by UV photons having different energies.

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Surface abundance change in vacuum ultraviolet photodissociation of CO2 and H2O mixture ices

Cited by 3 publications

References 40 publications

Quantification of O₂ formation during UV photolysis of water ice: H₂O and H₂O:CO₂ ices

Quantification of O₂ formation during UV photolysis of water ice: H₂O and H₂O:CO₂ ices

Division Xii / Commission 14 / Working Group Solids and Their Surfaces

Wavelength resolved UV photodesorption and photochemistry of CO₂ice

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Surface abundance change in vacuum ultraviolet photodissociation of CO2 and H2O mixture ices

Cited by 3 publications

References 40 publications

Quantification of O2 formation during UV photolysis of water ice: H2O and H2O:CO2 ices

Quantification of O2 formation during UV photolysis of water ice: H2O and H2O:CO2 ices

Division Xii / Commission 14 / Working Group Solids and Their Surfaces

Wavelength resolved UV photodesorption and photochemistry of CO2ice

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Quantification of O₂ formation during UV photolysis of water ice: H₂O and H₂O:CO₂ ices

Quantification of O₂ formation during UV photolysis of water ice: H₂O and H₂O:CO₂ ices

Wavelength resolved UV photodesorption and photochemistry of CO₂ice