Infrared Spectra of Dehydrogenated Carbon Molecules

Kuzmin, S.; Duley, W. W.

doi:10.48550/arxiv.1103.2989

Cited by 6 publications

(8 citation statements)

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“…The planar form of C 24 (graphene sheet) has recently been suggested to be the chemical carrier of three infrared bands at 6.6, 9.8 and 20.1 µm observed in the spectra of planetary nebulae, objects in the late stage of stellar evolution (1,2). This interpretation is supported by theoretical results of density functional theory (DFT), showing that the infrared transitions of planar C 24 match the observed band positions, and the fact that this isomer is likely to be more abundant in space since it is energetically more favourable than its fullerene form (3). However, more accurate calculations at the basis set limit of couple cluster (CCSD(T)) theory showed that these two isomers are equal in energy (4).…”

Section: Introductionmentioning

confidence: 66%

A theoretical investigation of the possible detection of C₂₄ in space

Sadjadi

Kwok

Cataldo

et al. 2020

Fullerenes, Nanotubes and Carbon Nanostructures

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Astronomical infrared spectral features at ~6.6, 9.8 and 20 µm have recently been suggested as being due to the planar graphene form of C 24 carbon cluster. Here we report density functional theory and coupled cluster calculations on wavefunctions stability, relative energies, and infrared spectra of four different types of C 24 isomers, including the graphene and fullerene forms. The types of vibrational motions under these bands are also discussed. Among the four isomers, we find that the astronomical data are best approximated by the graphene form of C 24 .

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Section: Introductionmentioning

confidence: 66%

A theoretical investigation of the possible detection of C₂₄ in space

Sadjadi

Kwok

Cataldo

et al. 2020

Fullerenes, Nanotubes and Carbon Nanostructures

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“…On the other hand, in the literature the vibrational modes and intensities are known for C 24 , a small graphene sheet Martin et al (1996). performed quantum-chemical computations for C 24 using the B3LYP DFT Kuzmin & Duley (2011). also carried out DFT-based calculations for planar C 24 and obtained similar…”

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confidence: 99%

On Graphene in the Interstellar Medium

Chen

Zhang

2017

ApJ

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The possible detection of C 24 , a planar graphene, recently reported in several planetary nebulae by García-Hernández et al. (2011 inspires us to explore whether and how much graphene could exist in the interstellar medium (ISM) and how it would reveal its presence through its ultraviolet (UV) extinction and infrared (IR) emission. In principle, interstellar graphene could arise from the photochemical processing of polycyclic aromatic hydrocarbon (PAH) molecules which are abundant in the ISM through a complete loss of their hydrogen atoms, and/or from graphite which is thought to be a major dust species in the ISM through fragmentation caused by grain-grain collisional shattering. Both quantum-chemical computations and laboratory experiments have shown that the exciton-dominated electronic transitions in graphene cause a strong absorption band near 2755Å. We calculate the UV absorption of graphene and place an upper limit of ∼ 5 ppm of C/H (i.e., ∼ 1.9% of the total interstellar C) on the interstellar graphene abundance. We also model the stochastic heating of graphene C 24 in the ISM, excited by single starlight photons of the interstellar radiation field and calculate its IR emission spectra. We also derive the abundance of graphene in the ISM to be < 5 ppm of C/H by comparing the model emission spectra with that observed in the ISM.

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“…We detected three IR emission features near the most pronounced theoretical IR emission features of planar C 24 (i.e., at ∼ 6.6, 9.8 and 20 µm, see e.g., Martin et al, 1996;Kuzmin & Duley, 2011;Chen et al, 2017, and references therein) towards all the four pointings (see Figure 2). In the following, we shall present the three components based on the mean spectrum in detail.…”

Section: The Spectramentioning

confidence: 71%

“…The data products for the short-low (SL) and long-low (LL) modules from the SSC pipeline (version 18.18) were used to produce the final merged spectra, making use of the four slits: SL2 (5.21 -7.56 µm) and SL1 (7.57 -14.28 µm) with resolution R ∼ 100, and LL2 (14.29 -20.66 µm) and LL1 (20.67 -38.00 µm) with resolution R ∼ 100 (see e.g., Simpson et al, 2007;Simpson, 2018). In particular, the SL2, SL1 and LL2 slits cover the wavelength regions of the most pronounced theoretical IR emission features of graphene C 24 (i.e., at ∼ 6.6, 9.8 and 20 µm, see e.g., Martin et al, 1996;Kuzmin & Duley, 2011;Chen et al, 2017, and references therein). We downloaded all the SL and LL data (103 pointings 4 ) toward Sgr B2 and used the software MATLAB to extract spectral information from the original data.…”

Section: Data Descriptionmentioning

confidence: 97%

“…Novoselov (see Novoselov et al, 2004) for which they received the 2010 Nobel Prize in physics. García-Hernández et al (2011a, 2012 first detected the unusual IR emission features at ∼ 6.6, 9.8, and 20 µm in several Galactic and extragalactic planetary nebulae (PNe), which are coincident with the strongest transitions of a planar graphene sheet C 24 theoretically predicted by Kuzmin & Duley (2011). 1 More recently, Chen et al (2017) have studied the UV absorption and IR emission of graphene C 24 .…”

Section: Introductionmentioning

confidence: 99%

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Unusual infrared emission toward Sgr B2: possible planar C₂₄

Chen

Xiang

Yang

et al. 2019

Res. Astron. Astrophys.

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Interstellar graphene could be present in the interstellar medium (ISM), resulting from the photochemical processing of polycyclic aromatic hydrocarbon (PAH) molecules and/or collisional fragmentation of graphitic particles. Indeed, by comparing the observed ultraviolet (UV) extinction and infrared (IR) emission of the diffuse ISM with that predicted for graphene, as much as ∼ 2% of the total interstellar carbon could have been locked up in graphene without violating the observational constraints. While the possible detection of planar C 24 , a small piece of a graphene sheet, has been reported towards several Galactic and extragalactic planetary nebulae, graphene has not yet been detected in interstellar environments. In this work, we search for the characteristic IR features of C 24 at ∼ 6.6, 9.8, 20 µm toward Sgr B2, a high-mass star formation region, and find a candidate target toward R.A. (J2000) = 267 • .05855 and Decl. (J2000) = −28 • .01479 in Sgr B2 whose Spitzer/IRS spectra exhibit three bands peaking at ∼ 6.637, 9.853 and 20.050 µm which appear to be coincident with that of C 24 . Possible features of C 60 are also seen in this region. The candidate region is a warm dust environment heated by massive stars or star clusters, associated with a WISE spot (a tracer of star-formation activity), close to the HII region candidate IRAS 17450-2759, and is surrounded by seven young stellar object candidates within ∼ 5 , suggesting that the creation and/or excitation of C 24 could be related to star formation activities.

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Infrared Spectra of Dehydrogenated Carbon Molecules

Cited by 6 publications

References 1 publication

A theoretical investigation of the possible detection of C₂₄ in space

A theoretical investigation of the possible detection of C₂₄ in space

On Graphene in the Interstellar Medium

Unusual infrared emission toward Sgr B2: possible planar C₂₄

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Infrared Spectra of Dehydrogenated Carbon Molecules

Cited by 6 publications

References 1 publication

A theoretical investigation of the possible detection of C24 in space

A theoretical investigation of the possible detection of C24 in space

On Graphene in the Interstellar Medium

Unusual infrared emission toward Sgr B2: possible planar C24

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A theoretical investigation of the possible detection of C₂₄ in space

A theoretical investigation of the possible detection of C₂₄ in space

Unusual infrared emission toward Sgr B2: possible planar C₂₄