On observing C60+and C602+in laboratory and space

Strelnikov, Dmitry; Kern, Bastian; Kappes, Manfred M.

doi:10.1051/0004-6361/201527234

Cited by 48 publications

(55 citation statements)

References 24 publications

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“…The value obtained in the neon matrix study, a factor of ten smaller than calculated, was underestimated because of ion loss during its growth. A recent experimental matrix isolation study (Strelnikov et al 2015) reports values in accord with the theoretical predictions.…”

Section: Introductionsupporting

confidence: 63%

Gas Phase Absorption Spectroscopy of and in a Cryogenic Ion Trap: Comparison With Astronomical Measurements*

Campbell

Holz

Maier

et al. 2016

ApJ

114

144

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Recent low-temperature laboratory measurements and astronomical observations have proved that the fullerene cation + C 60 is responsible for four diffuse interstellar bands (DIBs). These absorptions correspond to the strongest bands of the lowest electronic transition. The gas phase spectrum below 10 K is reported here for the full wavelength range encompassed by the electronic transition. The absorption spectrum of + C 70 , with its origin band at Å 7959.2 , has been obtained under similar laboratory conditions. Observations made toward the reddened star HD 183143 were used in a specific search for the absorption of these fullerene cations in diffuse clouds. In the case of + C 60 , one further band in the astronomical spectrum at Å 9348.5 is identified, increasing the total number of assigned DIBs to five. Numerous other + C 60 absorptions in the laboratory spectrum are found to lie below the astronomical detection limit. Special emphasis is placed on the laboratory determination of absolute absorption cross-sections. For + C 60 this directly yields a column density, ( ) + N C 60 , of´-2 10 cm 13 2 in diffuse clouds, without the need to rely on theoretical oscillator strengths. The intensity of the + C 70 electronic transition in the range 7000-8000 Å is spread over many features of similar strength. Absorption cross-section measurements indicate that even for a similar column density, the individual absorption bands of + C 70 will be too weak to be detected in the astronomical spectra, which is confirmed giving an upper limit of 2 mÅ to the equivalent width.

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Section: Introductionsupporting

confidence: 63%

Gas Phase Absorption Spectroscopy of and in a Cryogenic Ion Trap: Comparison With Astronomical Measurements*

Campbell

Holz

Maier

et al. 2016

ApJ

114

144

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“…With the confirmation of the C + 60 DIB identification and the new f -value provided in Ne matrix by Strelnikov et al (2015), the abundance of C + 60 can now be relatively accurately estimated in interstellar diffuse clouds. We have used for that 13 typical sight lines of diffuse clouds where these DIBs have been detected well (Galazutdinov et al 2000;see Fig.…”

Section: Interstellar Abundancesmentioning

confidence: 73%

“…3). While Campbell et al cannot measure accurate band strengths, improved f -values, for the corresponding bands in an Ne matrix, are provided by Strelnikov et al (2015), namely f = 0.015 ± 0.005 for the 966 nm absorption and f = 0.01 ± 0.003 for the 958 nm absorption. However, matrix effects could substantially affect line strengths, as possibly seen from the large difference between the line ratios measured by Strelnikov et Stepanov (2002).…”

Section: Ionsmentioning

confidence: 99%

Interstellar fullerene compounds and diffuse interstellar bands

Omont

2016

A&A

100

103

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Recently, the presence of fullerenes in the interstellar medium (ISM) has been confirmed and new findings suggest that these fullerenes may possibly form from polycyclic aromatic hydrocarbons (PAHs) in the ISM. Moreover, the first confirmed identification of two strong diffuse interstellar bands (DIBs) with the fullerene, C + 60 , connects the long standing suggestion that various fullerenes could be DIB carriers. These new discoveries justify reassessing the overall importance of interstellar fullerene compounds, including fullerenes of various sizes with endohedral or exohedral inclusions and heterofullerenes (EEHFs). The phenomenology of fullerene compounds is complex. In addition to fullerene formation in grain shattering, fullerene formation from fully dehydrogenated PAHs in diffuse interstellar clouds could perhaps transform a significant percentage of the tail of low-mass PAH distribution into fullerenes including EEHFs. But many uncertain processes make it extremely difficult to assess their expected abundance, composition and size distribution, except for the substantial abundance measured for C + 60 . EEHFs share many properties with pure fullerenes, such as C 60 , as regards stability, formation/destruction and chemical processes, as well as many basic spectral features. Because DIBs are ubiquitous in all lines of sight in the ISM, we address several questions about the interstellar importance of various EEHFs, especially as possible carriers of diffuse interstellar bands. Specifically, we discuss basic interstellar properties and the likely contributions of fullerenes of various sizes and their charged counterparts such as C + 60 , and then in turn: 1) metallofullerenes; 2) heterofullerenes; 3) fulleranes; 4) fullerene-PAH compounds; 5) H 2 @C 60 . From this reassessment of the literature and from combining it with known DIB line identifications, we conclude that the general landscape of interstellar fullerene compounds is probably much richer than heretofore realized. EEHFs, together with pure fullerenes of various sizes, have many properties necessary to be suitably carriers of DIBs: carbonaceous nature; stability and resilience in the harsh conditions of the ISM; existing with various heteroatoms and ionization states; relatively easy formation; few stable isomers; spectral lines in the right spectral range; various and complex energy internal conversion; rich Jahn-Teller fine structure. This is supported by the first identification of a DIB carrier as C + 60 . Unfortunately, the lack of any precise information about the complex optical spectra of EEHFs and most pure fullerenes other than C 60 and about their interstellar abundances still precludes definitive assessment of the importance of fullerene compounds as DIB carriers. Their compounds could significantly contribute to DIBs, but it still seems difficult that they are the only important DIB carriers. Regardless, DIBs appear as the most promising way of tracing the interstellar abundances of various fullerene compounds if the breakthr...

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“…The detections of interstellar C 60 and C 70 and their cations have also been reported based on their characteristic infrared (IR) emission features, e.g., the 7. 0, 8.45, 17.3 and 18.9 µm features of C 60 (Cami et al 2010, Sellgren et al 2010, Berné et al 2017, García-Hernández et al 2010) and the 6.4, 7.1, 8.2 and 10.5 µm features of C + 60 (Berné et al 2013, Strelnikov et al 2015. In addition, C + 60 has also been suggested as a promising carrier of the mysterious diffuse interstellar bands at 9348.4, 9365.2, 9427.8, 9577.0, and 9632.1Å (Foing & Ehrenfreund 1994, Campbell et al 2015, 2016, Walker et al 2015.…”

Section: Introductionmentioning

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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On observing C₆₀⁺and C₆₀²⁺in laboratory and space

Abstract: Recently, we have measured the IR absorptions of C

Cited by 48 publications

References 24 publications

Gas Phase Absorption Spectroscopy of and in a Cryogenic Ion Trap: Comparison With Astronomical Measurements*

Gas Phase Absorption Spectroscopy of and in a Cryogenic Ion Trap: Comparison With Astronomical Measurements*

Interstellar fullerene compounds and diffuse interstellar bands

On Graphene in the Interstellar Medium

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