Absorption spectroscopy of C60 molecules isolated in helium droplets

Close, John; Federmann, F.; Hoffmann, K.; Quaas, N.

doi:10.1016/s0009-2614(97)00870-1

Cited by 51 publications

(42 citation statements)

References 13 publications

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“…This band is accompanied by clearly resolved vibronic bands on the high-energy side. The excellent resolution obtained in helium droplets is illustrated in Figure 16 where the C 60 spectrum [216] is compared with spectra obtained in a neon matrix [217] and in a seeded beam. [218] The resolution of the droplet spectrum is much better than in the neon matrices and comparable to the seeded-beam spectrum.…”

Section: Electronic Excitation Spectramentioning

confidence: 98%

Superfluid Helium Droplets: A Uniquely Cold Nanomatrix for Molecules and Molecular Complexes

2004

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Herein, recent experiments on the spectroscopy and chemical reactions of molecules and complexes embedded in helium droplets are reviewed. In the droplets, a high spectroscopic resolution, which is comparable to the gas phase is achieved, while an isothermal low-temperature environment is maintained by evaporative cooling at T =0.37 K (4He droplets) or 0.15 K (3He droplets), lower than possible in most solid matrices. Thus the helium-droplet technique combines the benefits of both the gas phase and the classical matrix-isolation techniques. Most important, the superfluid helium facilitates binary encounters, and absorbs the released binding energy upon recombination. Thus the droplet can be viewed as an isothermal nanoscopic reactor, which isolates single molecules, clusters, or even a single reactive encounter at ultralow temperatures.

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Section: Electronic Excitation Spectramentioning

confidence: 98%

Superfluid Helium Droplets: A Uniquely Cold Nanomatrix for Molecules and Molecular Complexes

2004

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“…Various techniques have been used, including absorption spectroscopy in cold molecular beams (Haufler et al 1991;Hansen et al 1997) or He droplets (Close et al 1997), combined absorption and fluorescence spectroscopy in rare gas matrices (Sassara et al 1996a(Sassara et al , 1997Chergui 2000), phosphorescence (Sassara et al 1996b), fluorescence and phosphorescence from individual C 60 molecules excited by local electron tunneling (Cavar et al 2005).…”

Section: Appendix A: Interstellar Accretion Of C + To C 60mentioning

confidence: 99%

“…For identifying weak DIBs, the most interesting laboratory data are obviously absorption spectroscopy of Haufler et al (1991), Hansen et al (1997), Close et al (1997), and Sassara et al (1996a). Herzberg-Teller coupling with vibration states allows weak absorption in the forbidden transitions from the ground state h 10 u 1 A g to the first singlet excited states h 9 u t 1u 1 T 1g , 1 T 2g , and 1 G g .…”

Section: Appendix A: Interstellar Accretion Of C + To C 60mentioning

confidence: 99%

“…Checks with gas phase data are thus mandatory. But they are available only for a limited wavelength range, 5900−6300 Å (Haufler et al 1991;Hansen et al 1997) (as well as the He droplet data of Close et al 1997).…”

Section: Appendix A: Interstellar Accretion Of C + To C 60mentioning

confidence: 99%

“…However, as quoted by Herbig, this identification cannot be considered as secure, especially for such a weak DIB (EW = 6.9 mÅ/mag in HD 183143, Hobbs et al 2009). In addition, both Close et al (1997) and Hansen et al (1997) have said that there could be a problem in the wavelength recording of the preliminary spectrum shown in their Fig. 2 by Haufler et al The main problem seems to be in the blue part of the spectrum.…”

Section: Appendix A: Interstellar Accretion Of C + To C 60mentioning

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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