Solid state chemistry of nitrogen oxides – Part I: surface consumption of NO

It was in 'The Magellanic Cloud' (1955) -a science fiction novel by Stanislaw Lem -that engineers traveling to another star noticed that their spacecraft for unknown reasons overheated. The cause had to be outside the spaceship, but obviously there was only emptiness, at least compared to terrestrial conditions. The space between the stars, the interstellar medium, however, is not completely empty and at the high speed of the spacecraft the cross-section with impacting particles, even from such a dilute environment, was found to be sufficient to cause an overheating. Today, 60 years later, the interstellar medium has been studied in detail by astronomical observations, reproduced in dedicated laboratory experiments and simulated by complex astrochemical models. The space between the stars is, indeed, far from empty; it comprises gas, dust and ice and the molecules detected so far are both small (diatomics) and large (long carbon chains, PAHs and fullerenes), stable and reactive (radicals, ions, and excited molecules) evidencing an exotic and fascinating chemistry, taking place at low densities, low temperatures and experiencing intense radiation fields.Astrochemists explain the observed chemical complexity in space -so far 185 different molecules (not including isotopologues) have been identified -as the cumulative outcome of P a g e | 2 reactions in the gas phase and on icy dust grains. Gas phase models explain the observed abundances of a substantial part of the observed species, but fail to explain the number densities for stable molecules, as simple as water, methanol or acetonitrile -one of the most promising precursor species for the simplest amino acid glycine -as well as larger compounds such as glycolaldehyde, dimethylether and ethylene glycol. Evidence has been found that these and other complex species, including organic ones, form on icy dust grains that act as catalytic sites for molecule formation. It is here where particles 'accrete, meet, and greet' (i.e., freeze out, diffuse and react) upon energetic and non-energetic processing, such as irradiation by vacuum UV light, interaction with impacting particles (atoms, electrons and cosmic rays) or heating.This review paper summarizes the state-of-the-art in laboratory based interstellar ice chemistry. The focus is on atom addition reactions, illustrating how water, carbon dioxide and methanol can form in the solid state at astronomically relevant temperatures, and also the formation of more complex species such as hydroxylamine, an important prebiotic molecule, and glycolaldehyde, the smallest sugar, is discussed. These reactions are particularly relevant during the 'dark' ages of star and planet formation, i.e., when the role of UV light is restricted.A quantitative characterization of such processes is only possible through dedicated laboratory studies, i.e., under full control of a large set of parameters such as temperature, atom-flux, and ice morphology. The resulting numbers, physical and chemical constants, e.g., barrier heights, react...

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“…FIGURE 10 -The complete nitrogen chemistry network, summarizing the findings from [126][127][128][129][130][131][132][133][134].…”

Section: Surface Chemistry Of Nitrogen Bearing Moleculesmentioning

confidence: 99%

Atom addition reactions in interstellar ice analogues

Linnartz

Ioppolo

Fedoseev

2015

International Reviews in Physical Chemistry

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160

142

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“…2 for more details on TPD-QMS data). Along with traces of cis-(NO)2, also weak signals due to NO monomers can be resolved after UV-processing of the ice through their characteristic absorption at 1875 cm -1 (Fateley et al 1959, Fedoseev et al 2012, Minissale et al 2014. Wavelength, m Wavelength, m The total H-atom fluence is 6x10 16 atoms cm -2 .…”

Section: Simultaneous Hydrogenation and Uv-processing Of Pure Nomentioning

confidence: 99%

“…This is particularly important under the extremely cold conditions of the interstellar medium (ISM), where gas-phase and surface reactions are strongly affected by even small endothermicity or the presence of an activation barrier. Recently, frozen NO molecules have been linked to the formation of other species, like NH2OH, NO2, N2O, and HNO2 (Joshi et al 2012, Congiu et al 2012a, Congiu et al 2012b, Fedoseev et al 2012, Minissale et al 2014, Ioppolo et al 2014a. In space, NO molecules are primarly formed in the gas-phase through the reaction: N (g) + OH (g) → NO (g) + H (g) (1), (see Herbst & Klemperer 1973, McGonagle et al 1990, Gerin et al 1992.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous hydrogenation and UV-photolysis experiments of NO in CO-rich interstellar ice analogues; linking HNCO, OCN⁻, NH₂CHO, and NH₂OH

Fedoseev

Chuang

Dishoeck

et al. 2016

Mon. Not. R. Astron. Soc.

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The laboratory work presented here, simulates the chemistry on icy dust grains as typical for the "CO freeze-out stage" in dark molecular clouds. It differs from previous studies in that solid-state hydrogenation and vacuum UV-photoprocessing are applied simultaneously to co-depositing molecules. In parallel, the reactions at play are described for fully characterized laboratory conditions. The focus is on the formation of molecules containing both carbon and nitrogen atoms, starting with NO in CO-, H2CO-, and CH3OH-rich ices at 13 K. The experiments yield three important conclusions. 1. Without UV-processing hydroxylamine (NH2OH) is formed, as reported previously. 2. With UV-processing (energetic) NH2 is formed through photodissociation of NH2OH. This radical is key in the formation of species with an N-C bond. 3. The formation of three N-C bearing species, HNCO, OCN -and NH2CHO is observed. The experiments put a clear chemical link between these species; OCN -is found to be a direct derivative of HNCO and the latter is shown to have the same precursor as formamide (NH2CHO). Moreover, the addition of VUV competing channels decreases the amount of NO molecules converted into NH2OHby at least one order of magnitude. Consequently, this decrease in NH2OH formation yield directly influences the amount of NO molecules that can be converted into HNCO, OCN -and NH2CHO.

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“…7,8 Laboratory studies of non-energetic surface processing showed that, for instance, ammonia (NH 3 ), hydroxylamine (NH 2 OH), nitrogen dioxide (NO 2 ), dinitrogen trioxide (N 2 O 3 ), nitrous acid (HNO 2 ), and nitric acid (HNO 3 ) are efficiently formed at low temperatures through hydrogenation of N-atoms, NO + H, NO + O 2 , NO + NO 2 , NO + OH, and NO 2 + OH reactions, respectively. [9][10][11][12][13][14][15][16] In the accompanying paper, hereafter referred to as Part I, 17 we investigate the oxygenation of solid NO (NO + O/O 2 /O 3 ) at a Division of Geological and Planetary Sciences, California Institute of Technology,…”

Section: Introductionmentioning

confidence: 99%