Solid-state formation of CO<sub>2</sub>via the H<sub>2</sub>CO + O reaction

Minissale, Marco; Loison, Jean‐Christophe; Baouche, S.; Chaabouni, H.; Congiu, E.; Dulieu, F.

doi:10.1051/0004-6361/201424342

Cited by 30 publications

(28 citation statements)

References 64 publications

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“…More recently, the diffusion of O atoms was investigated on different substrates experimentally and theoretically at low (∼6 K) (Minissale et al 2013Congiu et al 2014;Lee & Meuwly 2014) and high surface temperatures (50 K) (Minissale et al 2015). Simultaneously, two experimental groups (Ward et al 2011;Kimber et al 2014;He et al 2015) proposed a rather high value for the adsorption energy of O atoms (i.e., 1500-1800 K) on different substrates, consistently with theoretical estimations by Bergeron et al (2008).…”

Section: Introductionsupporting

confidence: 60%

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Direct measurement of desorption and diffusion energies of O and N atoms physisorbed on amorphous surfaces

Minissale

Congiu

Dulieu

2016

A&A

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Context. Physisorbed atoms on the surface of interstellar dust grains play a central role in solid state astrochemistry. Their surface reactivity is one source of the observed molecular complexity in space. In experimental astrophysics, the high reactivity of atoms also constitutes an obstacle to measuring two of the fundamental properties in surface physics, namely desorption and diffusion energies, and so far direct measurements are non-existent for O and N atoms. Aims. We investigated the diffusion and desorption processes of O and N atoms on cold surfaces in order to give boundary conditions to astrochemical models. Methods. Here we propose a new technique for directly measuring the N-and O-atom mass signals. Including the experimental results in a simple model allows us to almost directly derive the desorption and diffusion barriers of N atoms on amorphous solid water ice (ASW) and O atoms on ASW and oxidized graphite. Results. We find a strong constraint on the values of desorption and thermal diffusion energy barriers. The measured barriers for O atoms are consistent with recent independent estimations and prove to be much higher than previously believed (E des = 1410−360 K on ASW). As for oxygen atoms, we propose that the combination E des − E dif = 1320-750 K is a sensible choice among the possible pairs of solutions. Also, we managed to measure the desorption and diffusion energy of N atoms for the first time (E des = 720 +160 −80 ; E dif = 525 +260 −200 K on ASW) in the thermal hopping regime and propose that the combination E des -E dif = 720-400 K can be reasonably adopted in models. The value of E dif for N atoms is slightly lower than previously suggested, which implies that the N chemistry on dust grains might be richer.

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Section: Introductionsupporting

confidence: 60%

“…The resulting desorption flux X · k X−des is proportional to the mass signal measured in the experiments. Finally, R(X, k X−dif ) represents a series of terms accounting for reactions involving particle X (Minissale et al , 2015, Notes. The E dif /E des ratio was fixed to 0.7.…”

Section: Discussionmentioning

confidence: 99%

Direct measurement of desorption and diffusion energies of O and N atoms physisorbed on amorphous surfaces

Minissale

Congiu

Dulieu

2016

A&A

Self Cite

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“…Thus such a CO2 ice-rich zone appears characteristic of the outer parts of the infall-dominated disc independent of the exact parameters used in the chemical model within the framework of the two-phase model considered here (although they do change the abundances quantatively). In fact, two additional pathways to CO2 have recently been experimentally verified, namely CO+O with EA = 1000 K and H2CO+O with EA = 335 K (Minissale et al 2013(Minissale et al , 2015. Currently, they are not included in the chemical network, but are expected to positively contribute to the CO2 production.…”

Section: Diffusion and Quantum Tunneling Barriersmentioning

confidence: 99%

Cometary ices in forming protoplanetary disc midplanes

Drozdovskaya¹,

Walsh²,

Dishoeck³

et al. 2016

Mon. Not. R. Astron. Soc.

101

137

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Low-mass protostars are the extrasolar analogues of the natal Solar System. Sophisticated physicochemical models are used to simulate the formation of two protoplanetary discs from the initial prestellar phase, one dominated by viscous spreading and the other by pure infall. The results show that the volatile prestellar fingerprint is modified by the chemistry en route into the disc. This holds relatively independent of initial abundances and chemical parameters: physical conditions are more important. The amount of CO 2 increases via the grain-surface reaction of OH with CO, which is enhanced by photodissociation of H 2 O ice. Complex organic molecules are produced during transport through the envelope at the expense of CH 3 OH ice. Their abundances can be comparable to that of methanol ice (few % of water ice) at large disc radii (R > 30 AU). Current Class II disc models may be underestimating the complex organic content. Planet population synthesis models may underestimate the amount of CO 2 and overestimate CH 3 OH ices in planetesimals by disregarding chemical processing between the cloud and disc phases. The overall C/O and C/N ratios differ between the gas and solid phases. The two ice ratios show little variation beyond the inner 10 AU and both are nearly solar in the case of pure infall, but both are sub-solar when viscous spreading dominates. Chemistry in the protostellar envelope en route to the protoplanetary disc sets the initial volatile and prebiotically-significant content of icy planetesimals and cometary bodies. Comets are thus potentially reflecting the provenances of the midplane ices in the Solar Nebula.

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“…Dulieu et al 2013;Minissale et al 2015Minissale et al , 2016. The solid species that we consider in the code to model the dust chemistry are listed in Table 2.…”

Section: Dust Chemistrymentioning

confidence: 99%

Surface chemistry in photodissociation regions

Esplugues

Cazaux

Meijerink

et al. 2016

A&A

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Context. The presence of dust can strongly affect the chemical composition of the interstellar medium. We model the chemistry in photodissociation regions (PDRs) using both gas-phase and dust-phase chemical reactions. Aims. Our aim is to determine the chemical compositions of the interstellar medium (gas/dust/ice) in regions with distinct (molecular) gas densities that are exposed to radiation fields with different intensities. Methods. We have significantly improved the Meijerink PDR code by including 3050 new gas-phase chemical reactions and also by implementing surface chemistry. In particular, we have included 117 chemical reactions occurring on grain surfaces covering different processes, such as adsorption, thermal desorption, chemical desorption, two-body reactions, photo processes, and cosmicray processes on dust grains. Results. We obtain abundances for different gas and solid species as a function of visual extinction, depending on the density and radiation field. We also analyse the rates of the formation of CO 2 and H 2 O ices in different environments. In addition, we study how chemistry is affected by the presence/absence of ice mantles (bare dust or icy dust) and the impact of considering different desorption probabilities. Conclusions. The type of substrate (bare dust or icy dust) and the probability of desorption can significantly alter the chemistry occurring on grain surfaces, leading to differences of several orders of magnitude in the abundances of gas-phase species, such as CO, H 2 CO, and CH 3 OH. The type of substrate, together with the density and intensity of the radiation field, also determine the threshold extinction to form ices of CO 2 and H 2 O. We also conclude that H 2 CO and CH 3 OH are mainly released into the gas phase of low, far-ultraviolet illuminated PDRs through chemical desorption upon two-body surface reactions, rather than through photodesorption.

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Solid-state formation of CO₂via the H₂CO + O reaction

Cited by 30 publications

References 64 publications

Direct measurement of desorption and diffusion energies of O and N atoms physisorbed on amorphous surfaces

Direct measurement of desorption and diffusion energies of O and N atoms physisorbed on amorphous surfaces

Cometary ices in forming protoplanetary disc midplanes

Surface chemistry in photodissociation regions

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Solid-state formation of CO2via the H2CO + O reaction

Cited by 30 publications

References 64 publications

Direct measurement of desorption and diffusion energies of O and N atoms physisorbed on amorphous surfaces

Direct measurement of desorption and diffusion energies of O and N atoms physisorbed on amorphous surfaces

Cometary ices in forming protoplanetary disc midplanes

Surface chemistry in photodissociation regions

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Solid-state formation of CO₂via the H₂CO + O reaction