SMALL CARBONACEOUS MOLECULES, ETHYLENE OXIDE (c-C2H4O) AND CYCLOPROPENYLIDENE (c-C3H2): SOURCES OF THE UNIDENTIFIED INFRARED BANDS?

Bernstein, Lawrence S.; Lynch, D. K.

doi:10.1088/0004-637x/704/1/226

Cited by 35 publications

(31 citation statements)

References 68 publications

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“…The structure of the 10-µm feature and presence of forsterite bands at 23.3, 27.8, and 33.7 µm suggest that the dust was formed some time ago and already processed by stellar radiation. Objects with late-B/early-A spectral type stars also exhibit emission features which are attributed to Polycyclic Aromatic Hydrocarbons (Leger & Puget 1984) or to Small Carbonaceous Molecules (Bernstein & Lynch 2009). The IR flux level of all the objects is comparable with that of earlier observations (MSX, IRAS).…”

Section: Spitzer Datasupporting

confidence: 75%

Properties of the circumstellar dust in galactic FS CMa objects

et al. 2010

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Abstract. FS CMa objects are a group of hot stars that exhibit the B[e] phenomenon. The group was defined a few years ago on the basis of the formerly known unclassified B[e] stars and newly discovered objects. One of their main features is the presence of hot circumstellar dust whose properties were unknown. We present IR spectra of nearly 20 FS CMa objects obtained with the Spitzer Space Telescope. Dusty features, such as broad silicate bands in emission and narrow bands that are usually explained by PAHs, are detected. The IR fluxes are compared to those detected by IRAS and MSX. Main results of the data analysis are briefly discussed.

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Section: Spitzer Datasupporting

confidence: 75%

Properties of the circumstellar dust in galactic FS CMa objects

et al. 2010

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“…However, in the low-density ISM all of these bands lie within wavelength regions that will be dominated by the aromatic-rich material IR emission bands and the epoxide bands will therefore be masked by other more abundant IR dust features (figure 11). Indeed, it has been shown that the IR spectroscopy of small carbonaceous molecules, such as ethylene oxide (c-C 2 H 4 O) and cyclopropenylidene (c-C 3 H 2 ), shows a remarkably interesting correspondence with most of the so-called aromatic emission bands [94]. Further, it has been proposed that ethylene oxide is formed and retained on carbonaceous grain surfaces, precluding the radio detection of its rotational lines [94].…”

Section: Dust: Evolutionary Consequencesmentioning

confidence: 99%

Dust evolution, a global view: III. Core/mantle grains, organic nano-globules, comets and surface chemistry

Jones¹

2016

R. Soc. open sci.

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Within the framework of The Heterogeneous dust Evolution Model for Interstellar Solids (THEMIS), this work explores the surface processes and chemistry relating to core/mantle interstellar and cometary grain structures and their influence on the nature of these fascinating particles. It appears that a realistic consideration of the nature and chemical reactivity of interstellar grain surfaces could self-consistently and within a coherent framework explain: the anomalous oxygen depletion, the nature of the CO dark gas, the formation of ‘polar ice’ mantles, the red wing on the 3 μm water ice band, the basis for the O-rich chemistry observed in hot cores, the origin of organic nano-globules and the 3.2 μm ‘carbonyl’ absorption band observed in comet reflectance spectra. It is proposed that the reaction of gas phase species with carbonaceous a-C(:H) grain surfaces in the interstellar medium, in particular the incorporation of atomic oxygen into grain surfaces in epoxide functional groups, is the key to explaining these observations. Thus, the chemistry of cosmic dust is much more intimately related with that of the interstellar gas than has previously been considered. The current models for interstellar gas and dust chemistry will therefore most likely need to be fundamentally modified to include these new grain surface processes.

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“…Acetaldehyde has been observed in translucent clouds (Turner et al 1999), cold molecular clouds (Matthews et al 1985;Turner et al 1999), and star-forming regions (Bell et al 1983;Charnley 2004;Fourikis et al 1974;Ikeda et al 2001;Nummelin et al 1998;Turner 1991;Ziurys & McGonagle 1993). Ethylene oxide has been detected toward hot cores (Dickens et al 1997;Ikeda et al 2001;Nummelin et al 1998) and has recently been proposed as a carrier of the unidentified infrared bands (Bernstein & Lynch 2009). Vinyl alcohol has been observed in the hot core Sgr B2N (Turner & Apponi 2001), a source in which all three of the C 2 H 4 O isomers have been identified.…”

Section: Introductionmentioning

confidence: 99%

Thermal Reactions of Oxygen Atoms With Alkenes at Low Temperatures on Interstellar Dust

Ward

Price²

2011

ApJ

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Laboratory experiments show that the thermal heterogeneous reactions of oxygen atoms may contribute to the synthesis of epoxides in interstellar clouds. The data set also indicates that the contribution of these pathways to epoxide formation, in comparison to non-thermal routes, is likely to be strongly temperature dependent. Our results indicate that an increased abundance of epoxides, relative to the corresponding aldehydes, could be an observational signature of a significant contribution to molecular oxidation via thermal O atom reactions with alkenes. Specifically surface science experiments show that both C 2 H 4 O and C 3 H 6 O are readily formed from reactions of ethene and propene molecules with thermalized oxygen atoms at temperatures in the range of 12-90 K. It is clear from our experiments that these reactions, on a graphite surface, proceed with significantly reduced reaction barriers compared with those operating in the gas phase. For both the C 2 H 4 + O and the C 3 H 6 + O reactions, the surface reaction barriers we determine are reduced by approximately an order of magnitude compared with the barriers in the gas phase. The modeling of our experimental results, which determines these reaction barriers, also extracts desorption energies and rate coefficients for the title reactions. Our results clearly show that the major product from the O + C 2 H 4 reaction is ethylene oxide, an epoxide.

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SMALL CARBONACEOUS MOLECULES, ETHYLENE OXIDE (c-C₂H₄O) AND CYCLOPROPENYLIDENE (c-C₃H₂): SOURCES OF THE UNIDENTIFIED INFRARED BANDS?

Cited by 35 publications

References 68 publications

Properties of the circumstellar dust in galactic FS CMa objects

Properties of the circumstellar dust in galactic FS CMa objects

Dust evolution, a global view: III. Core/mantle grains, organic nano-globules, comets and surface chemistry

Thermal Reactions of Oxygen Atoms With Alkenes at Low Temperatures on Interstellar Dust

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