The puzzling behavior of HNCO isomers in molecular clouds

Marcelino, N.; Brünken, Sandra; Cernicharo, J.; Quan, Donghui; Roueff, E.; Herbst, Eric; Thaddeus, P.

doi:10.1051/0004-6361/200913806

Cited by 65 publications

(105 citation statements)

References 41 publications

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“…From the present observations, it cannot be conclusively decided whether grain-surface chemistry plays a dominant role in the synthesis of CHNO isomers. Pure gas-phase chemical models, based on the steady-state approach used by Marcelino et al (2009), and extended by reactions involving protonated forms of NCO, CNO, and of the four stable CHNO isomers, predict HNCO to HOCN abundance ratios matching the observed values stated in Table 3 for the Galactic center clouds (Marcelino et al 2010) The abundances of HNCO and its isomers are governed by a complex network of surface and gas-phase formation and destruction reactions. Further observations of HOCN toward additional regions of the interstellar medium rich in HNCO such as other high-mass star-forming regions, young stellar objects (YSOs), and dense cloud cores -and the observation of HOCN in sources where HCNO has been detected and vice versa -will help to further constrain the interstellar chemistry of this isomeric system.…”

Section: Discussionmentioning

confidence: 66%

Interstellar HOCN in the Galactic center region

Brünken¹,

Беллоче

Martín

et al. 2010

A&A

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Aims. Our aim is to confirm the interstellar detection of cyanic acid, HOCN, in the Galactic center clouds. It has previously been tentatively detected only in Sgr B2(OH). Methods. We used a complete line survey of the hot cores Sgr B2(N) and (M) in the 3 mm range, complemented by additional observations carried out with the IRAM 30 m telescope at selected frequencies in the 2 mm band and towards four additional positions in the Sgr B2 cloud complex in the 2 and 3 mm bands. The spectral survey was analysed in the local thermodynamical equilibrium approximation (LTE) by modeling the emission of all identified molecules simultaneously. This allowed us to distinguish weak features of HOCN from the rich line spectrum observed in Sgr B2(N) and (M). Lines of the more stable (by 1.1 eV) isomer isocyanic acid, HNCO, in these sources, as well as those of HOCN and HNCO towards the other positions, were analysed in the LTE approximation as well. Results. Four transitions of HOCN were detected in a quiescent molecular cloud in the Galactic center at a position offset in (RA, Dec) by (20 , 100 ) from the hot core source Sgr B2(M), confirming its previous tentative interstellar detection. Up to four transitions were detected toward five other positions in the Sgr B2 complex, including the hot cores Sgr B2(M), (S), and (N). A fairly constant abundance ratio of ∼0.3−0.8% for HOCN relative to HNCO was derived for the extended gas components, suggesting a common formation process of these isomers.

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Section: Discussionmentioning

confidence: 66%

Interstellar HOCN in the Galactic center region

Brünken¹,

Беллоче

Martín

et al. 2010

A&A

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“…Observations towards different regions of Sgr B2 and towards several sources showed the same trend with HOCN/HNCO varying in the range of 0.003 to 0.03 Marcelino et al 2010). Specifically, a difference is observed between the cold and hot sources, with the former having on average an abundance ratio HNCO/HOCN smaller than the latter.…”

Section: Previous Observations Of the Chon Isomersmentioning

confidence: 58%

“…The third isomer on the energy scale, HCNO, was detected in dark cloud cores and in a lukewarm corino, but remains undetected towards Sgr B2 and molecular shocks (Marcelino et al 2009(Marcelino et al , 2010Mendoza et al 2014). The same dichotomy, even more pronounced (by one order of magnitude) is observed for the abundance ratio HNCO/HCNO between cold and warm sources.…”

Section: Previous Observations Of the Chon Isomersmentioning

confidence: 59%

“…Following this detection, which was seen as the first example of a peptide bond, a systematic search was carried out in a wide variety of environments. Thus, HNCO was detected in cold dense cores (Brown 1981;Marcelino et al 2009Marcelino et al , 2010Lopéz-Sepulcre et al 2015), in hot cores (Snyder & Buhl 1972;Churchwell et al 1986;Martin et al 2008) and hot corinos (Lopéz-Sepulcre et al 2015), in photon-dominated regions (Jansen et al 1995), in diffuse clouds (Turner et al 1999), in the direction of the Galactic center (Kuan & Snyder 1996;Cummins et al 1986;Turner 1991;Martin et al 2008), in molecular shocks (Mendoza et al 2014), and in external galaxies (Meier & Turner 2005;Martin et al 2008).…”

Section: Previous Observations Of the Chon Isomersmentioning

confidence: 97%

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Differential adsorption of CHON isomers at interstellar grain surfaces

Lattelais

Pauzat

Ellinger

et al. 2015

A&A

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Context. The CHON generic chemical formula covers different isomers such as isocyanic acid (HNCO), cyanic acid (HOCN), fulminic acid (HCNO), and isofulminic acid (HONC); the first three have been identified in a large variety of environments in the interstellar medium (ISM). Several phenomena could be at the origin of the observed abundances, such as different pathways of formation and destruction involving gas phase reactions with different possible activation barriers and/or surface processes depending on the local temperature and the nature of the support. Aims. The scope of this article is to shed some light on the interaction of the CHON isomers with interstellar grains as a function of the nature of the surface and to determine the corresponding adsorption energies in order to find whether this phenomenon could play a role in the abundances observed in the ISM. Methods. The question was addressed by means of numerical simulations using first principle periodic density functional theory (DFT) to represent the grain support as a solid of infinite dimension. Results. Regardless of the nature of the model surface (water ice, graphene, silica), two different classes of isomers were identified: weakly bound (HNCO and HCNO) and strongly bound (HOCN and HONC), with the adsorption energies of the latter group being about twice those of the former. The range of the adsorption energies is (from highest to lowest) HOCN > HONC > HNCO > HCNO. They are totally disconnected from the relative stabilities, which range from HNCO > HOCN > HCNO > HONC. Conclusions. The possibility of hydrogen bonding is the discriminating factor in the trapping of CHON species on grain surfaces. Whatever the environment, differential adsorption is effective and its contribution to the molecular abundances should not be ignored. The theoretical adsorption energies provided here could be profitably used for a more realistic modeling of molecule-surfaces interactions.

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“…Furthermore, the detection of several isomeric forms of molecules sharing the same raw chemical formula becomes now possible. The comparison of abundances of those isomers provides strong constraints on the chemical networks, as discussed by Marcelino et al [40] for the case of HNCO and its isomers HOCN and HCON.…”

Section: Probing Chemical Processes Isomersmentioning

confidence: 99%

Open problems and perspectives offered by current and future instruments

Gérin

2011

EPJ Web of Conferences

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Abstract. We summarize recent observational and theoretical results and discuss the open challenges for astrochemistry and the promises offered by the current and upcoming instruments. Some of the main challenges are listed below. -Characterization of the structure of the interstellar medium -Coupling of the matter with magnetic fields, role of cosmic rays -Coupling of the dynamics with the evolution of matter (chemistry, ionization degree, depletion, desorption) -Characterization of dust grains (composition, size, emissivity, polarization) -Evolution of the carbonaceous matter, PAHs, aggregates and Diffuse Interstellar Bands (DIBs) carriers -Oxygen chemistry and the low abundance of molecular oxygen -Nitrogen chemistry and its seeds, the nitrogen hydrides -Sulfur chemistry and the contribution of S + to the charge balance of translucent matter -Neutral-neutral reactions involving simple radicals (CH, CH 2 , OH, etc.).

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The puzzling behavior of HNCO isomers in molecular clouds

Cited by 65 publications

References 41 publications

Interstellar HOCN in the Galactic center region

Interstellar HOCN in the Galactic center region

Differential adsorption of CHON isomers at interstellar grain surfaces

Open problems and perspectives offered by current and future instruments

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