One- and two-photon absorptions of the Cn and Cn−1 Si fullerenes in gas phase and solution

Lan, You‐Zhao; Kang, Honglan; Niu, Tao

doi:10.1140/epjd/e2015-50789-0

Cited by 6 publications

(5 citation statements)

References 58 publications

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“…This might be important when considering DIB carriers, since they might have smaller LUMO-HOMO gaps and richer optical spectra than C 60 . But their known optical absorption spectra generally do not display prominent features in the visible range (Koponen et al 2008;Lan, Kang & Niu 2015). Such calculated data seem to still be lacking for most of their cations.…”

Section: And Other Fullerenesmentioning

confidence: 98%

“…The LUMO-HOMO gaps are smaller. The first visible allowed optical transitions appear then at longer wavelength; however, they remain relatively weak (Koponen et al 2008;Lan, Kang & Niu 2015) and no results seem available for cations. Similarly, the ionization potentials decrease by about 0.5-0.7 eV per Si atom (Tenorio & Robles 2000).…”

Section: Si and Other Silafullerenesmentioning

confidence: 99%

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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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Section: And Other Fullerenesmentioning

confidence: 98%

Section: Si and Other Silafullerenesmentioning

confidence: 99%

Interstellar fullerene compounds and diffuse interstellar bands

Omont

2016

A&A

100

103

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“…Fullerenes and their cations are known to have only relatively weak bands in the visible range (Koponen et al 2008;Lan et al 2015). However, no detailed laboratory or theoretical data about the optical spectrum of fullerenes except for C 60 and C 70 are available, including those with N C in the range 40-50, which we propose are the most likely possible products of PAH dehydrogenation.…”

Section: Fullerene Optical Spectramentioning

confidence: 90%

Intermediate-size fullerenes as degradation products of interstellar polycyclic aromatic hydrocarbons

Omont

Bettinger

2021

A&A

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The high interstellar abundances of polycyclic aromatic hydrocarbons (PAHs) and their size distribution are the result of complex chemical processes implying dust, UV radiation, and the main gaseous components (H, C+, and O). These processes must explain the high abundance of relatively small PAHs in the diffuse interstellar medium (ISM) and imply the continuous formation of some PAHs that are small enough (number of carbon atoms NC < ~35–50) to be completely dehydrogenated by interstellar UV radiation. The carbon clusters Cn thus formed are constantly exposed to the absorption of ~10–13.6 eV UV photons, allowing isomerization and favoring the formation of the most stable isomers. They might tend to form irregular carbon cages. The frequent accretion of interstellar C+ ions could favor further cage isomerization, as is known in the laboratory for C60, possibly yielding most stable fullerenes, such as C40, C44, and C50. These fullerenes are expected to be very stable in the diffuse ISM because C2 ejection is not possible by single UV photon absorption, but could need rare two-photon absorption. It is possible that at least one of these fullerenes or its cation is as abundant as C60 or C60+ in the diffuse ISM, although this abundance is limited by the lack of observed matching features in observed mid-infrared spectra. B3LYP calculations of the visible spectrum for a number of fullerene isomers with 40 ≤NC ≤ 50 show that they generally have a few spectral bands in the visible range, with f-values in the range of a few 10−2. This could make such fullerenes interesting candidates for the carriers of some diffuse interstellar bands.

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“…Fullerenes and their cations are known to have only relatively weak bands in the visible range (Koponen et al 2008;Lan, Kang & Niu 2015). However, no detailed laboratory or theoretical data about the optical spectrum of fullerenes except for C 60 and C 70 are available, including those with N C in the range 40-50, which we propose are the most likely possible products of PAH dehydrogenation.…”

Section: Fullerene Optical Spectramentioning

confidence: 90%

Intermediate-size fullerenes as degradation products of interstellar PAHs

Omont,

Bettinger

2021

Preprint

View full text Add to dashboard Cite

The high interstellar abundances of polycyclic aromatic hydrocarbons (PAHs) and their size distribution are the result of complex chemical processes implying dust, UV radiation, and the main gaseous components (H, C + , and O). These processes must explain the high abundance of relatively small PAHs in the diffuse interstellar medium (ISM) and imply the continuous formation of some PAHs that are small enough (number of carbon atoms N C <∼ 35-50) to be completely dehydrogenated by interstellar UV radiation. The carbon clusters C n thus formed are constantly exposed to the absorption of ∼10-13.6 eV UV photons, allowing isomerization and favoring the formation of the most stable isomers. They might tend to form irregular carbon cages. The frequent accretion of interstellar C + ions could favor further cage isomerization, as is known in the laboratory for C 60 , possibly yielding most stable fullerenes, such as C 40 , C 44 , and C 50 . These fullerenes are expected to be very stable in the diffuse ISM because C 2 ejection is not possible by single UV photon absorption, but could need rare two-photon absorption. It is possible that at least one of these fullerenes or its cation is as abundant as C 60 or C + 60 in the diffuse ISM, although this abundance is limited by the lack of observed matching features in observed mid-infrared spectra. B3LYP calculations of the visible spectrum for a number of fullerene isomers with 40 ≤ N C ≤ 50 show that they generally have a few spectral bands in the visible range, with f-values in the range of a few 10 −2 . This could make such fullerenes interesting candidates for the carriers of some diffuse interstellar bands.

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One- and two-photon absorptions of the Cn and Cn−1 Si fullerenes in gas phase and solution

Cited by 6 publications

References 58 publications

Interstellar fullerene compounds and diffuse interstellar bands

Interstellar fullerene compounds and diffuse interstellar bands

Intermediate-size fullerenes as degradation products of interstellar polycyclic aromatic hydrocarbons

Intermediate-size fullerenes as degradation products of interstellar PAHs

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