Mixed aromatic–aliphatic organic nanoparticles as carriers of unidentified infrared emission features

Kwok, Sun; Zhang, Yong

doi:10.1038/nature10542

Cited by 270 publications

(200 citation statements)

References 28 publications

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“…At the same time, since we do detect the A10, page 4 of 5 PAH features in the halo, a significant amount of PAHs including very small ones must be protected in dense molecular clouds against shocks in the halo. Alternatively, Kwok & Zhang (2011) pointed out that mixed aromatic-aliphatic organic nanoparticles can be carriers of both 3.3 and 3.4-3.6 μm features. In this case, the observed unusual features may simply reflect the processing of these nanoparticles.…”

Section: Discussionmentioning

confidence: 99%

AKARI near-infrared spectroscopy of the aromatic and aliphatic hydrocarbon emission features in the galactic superwind of M 82

Yamagishi

Kaneda

Ishihara

et al. 2012

A&A

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Aims. We investigate the properties of hydrocarbon grains in the galactic superwind of M 82. Methods. With AKARI, we performed near-infrared (2.5-4.5 μm) spectroscopic observations of 34 regions in M 82 including its northern and southern halos. Results. Many of the spectra show strong emission at 3.3 μm caused by polycyclic aromatic hydrocarbons (PAHs) and relatively weak features at 3.4-3.6 μm caused by aliphatic hydrocarbons. In particular, we clearly detect the PAH 3.3 μm emission and the 3.4-3.6 μm features in halo regions, which are located at a distance of 2 kpc away from the galactic center. We find that the ratios of the 3.4-3.6 μm features to the 3.3 μm feature intensity significantly increase with distance from the galactic center, while the ratios of the 3.3 μm feature to the AKARI 7 μm band intensity do not. Conclusions. Our results clearly confirm the presence of small PAHs even in the harsh environment of the halo of M 82. The results also reveal that the aliphatic hydrocarbons emitting the 3.4-3.6 μm features are unusually abundant in the halo, suggesting that small carbonaceous grains are produced by shattering of larger grains in the galactic superwind.

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Section: Discussionmentioning

confidence: 99%

AKARI near-infrared spectroscopy of the aromatic and aliphatic hydrocarbon emission features in the galactic superwind of M 82

Yamagishi

Kaneda

Ishihara

et al. 2012

A&A

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“…Kwok & Zhang (2011) argued that the material responsible for the UIE features may have a substantial aliphatic component and therefore, by definition, PAHs can not be the UIE carrier. This argument can be tested by examining the ratio of the observed intensity of the 3.3 µm feature (I 3.3 ) to that of the 3.4 µm feature (I 3.4 ) of UIE sources.…”

Section: Introductionmentioning

confidence: 99%

Polycyclic Aromatic Hydrocarbons with Aliphatic Sidegroups: Intensity Scaling for the C–H Stretching Modes and Astrophysical Implications

Yang

Glaser

et al. 2017

ApJ

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The so-called unidentified infrared emission (UIE) features at 3. 3, 6.2, 7.7, 8.6, and 11.3 µm ubiquitously seen in a wide variety of astrophysical regions are generally attributed to polycyclic aromatic hydrocarbon (PAH) molecules. Astronomical PAHs may have an aliphatic component as revealed by the detection in many UIE sources of the aliphatic C-H stretching feature at 3.4 µm. The ratio of the observed intensity of the 3.4 µm feature to that of the 3.3 µm aromatic C-H feature allows one to estimate the aliphatic fraction of the UIE carriers. This requires the knowledge of the intrinsic oscillator strengths of the 3.3 µm aromatic C-H stretch (A 3.3 ) and the 3.4 µm aliphatic C-H stretch (A 3.4 ). Lacking experimental data on A 3.3 and A 3.4 for the UIE candidate materials, one often has to rely on quantum-chemical computations. Although the second-order Møller-Plesset (MP2) perturbation theory with a large basis set is more accurate than the B3LYP density functional theory, MP2 is computationally very demanding and impractical for large molecules. Based on methylated PAHs, we show here that, by scaling the band strengths computed at an inexpensive level (e.g., B3LYP/6-31G * ) we are able to obtain band strengths as accurate as that computed at far more expensive levels (e.g., MP2/6-311+G(3df,3pd)). We calculate the model spectra of methylated PAHs and their cations excited by starlight of different spectral shapes and intensities. We find (I 3.4 /I 3.3 ) mod , the ratio of the model intensity of the 3.4 µm feature to that of the 3.3 µm feature, is insensitive to the spectral shape and intensity of the exciting starlight. We derive a straightforward relation for determining the aliphatic fraction of the UIE carriers (i.e., the ratio of the number of C atoms in aliphatic units N C,ali to that in aromatic rings N C,aro ) from the observed band ratios (I 3.4 /I 3.3 ) obs : N C,ali /N C,aro ≈ 0.57 × (I 3.4 /I 3.3 ) obs for neutrals and N C,ali /N C,aro ≈ 0.26 × (I 3.4 /I 3.3 ) obs for cations.

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“…Nevertheless already now there are data and facts of the astrophysics, confirming ideas of presented article. In this regard the data obtained in 2011 by Sun Kwok, and Yong Zhang (astrophysics from university of Hong Kong) on interpretation of the unknown infrared radiation (Unidentified Infrared Emission) of the interstellar environment in a fog Orion (Sun, 2013;Sun & Yong, 2011) are interesting. IR spectrums of the interstellar environment testify to existence of substances, which are the analogs of oil pitches and asphaltenes.…”

Section: Resultsmentioning

confidence: 99%

About Organic Systems Origin According to Equilibrium Thermodynamic Modeles of Molecules Distribution in Interstellar Medium

Dolomatov¹,

Zhuravliova

Tanatarova³

2014

APR

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Problem of an natural organic systems origin -amino acids, nucleotides and other construction elements of life and also natural hydrocarbonic systems to which oil and gas belong is actual not only with fundamental, but also from the practical point of view. We know that hydrocarbonic resources of a planet are steadily exhausted. At present there are not methods and models to calculate the resources of oil and life-related molecules in interstellar environment. In this paper is developed the mathematical model of the molecules composition distribution in the interstellar environment on thermodynamic potentials using methods of the probability theory, the mathematical and physical statistics and the equilibrium thermodynamics. Based on this model are estimated the resources of life-related molecules, amino acids and the nitrogenous bases in the interstellar medium. The possibility of the oil hydrocarbons molecules formation is shown. The given calculations confirm Sokolov's and Hoyl's hypotheses about the possibility of the oil hydrocarbons formation in Space. Results are confirmed by data of astrophysical supervision and space researches.

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Mixed aromatic–aliphatic organic nanoparticles as carriers of unidentified infrared emission features

Cited by 270 publications

References 28 publications

AKARI near-infrared spectroscopy of the aromatic and aliphatic hydrocarbon emission features in the galactic superwind of M 82

AKARI near-infrared spectroscopy of the aromatic and aliphatic hydrocarbon emission features in the galactic superwind of M 82

Polycyclic Aromatic Hydrocarbons with Aliphatic Sidegroups: Intensity Scaling for the C–H Stretching Modes and Astrophysical Implications

About Organic Systems Origin According to Equilibrium Thermodynamic Modeles of Molecules Distribution in Interstellar Medium

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