Absorption carbon onions

In the cosmos, however, carbon onions possibly exist. Soon after their discovery they have already been discussed as a potential reason for an up to then not interpretable absorption at 217.5 nm in the spectrum of interstellar space. The absorption spectrum of carbon onions closely resembles that of interstellar dust indeed. A red shift is observed on the occasion, yet this may be explained by the measurements being made in different media (water or vacuum, respectively Section 4.4.1.3). 

Numerous spectroscopic methods have been applied to examine the physical properties and to elucidate the structure of carbon onions. They include IR- and Raman spectroscopy. X-ray diffraction, electron energy loss spectroscopy (EELS), absorption, and photoluminescence spectroscopy and NMR-spectroscopy. Each of these methods gives account of certain aspects of the geometric and electronic structure, so altogether quite a detailed picture is obtained of the situation in carbon onions and related materials. There is, however, a strong dependency on... 

Absorption Spectra of Carbon Onions and Reiated Materiais... 

Soon after the discovery of carbon onions, their absorption behavior has been studied both in visible and UV hghL One motivation to do so was the assumption that they might be the long-sought source of an absorption band at 217.5 nm (4.60 (tm ) in the spectrum of interstellar dust. 

Figure 4.35 The absorption spectra of interstellar dust (a) and of carbon onions (b). It is true that the position of the absorption maximum is slightly shifted,...

Synthesis of carbon onions through heat treatment of soot by de Heer and Ugarte represented the first approach in producing carbon onions in macroscopic quantities. This is an important requirement for many further characterization steps and for any potential applications of this material. These carbon onions consist of hollow carbon onions, with between 2 and 8 graphitic shells, and their production in macroscopic quantities by this experimental approach enabled their examination by ultraviolet-visible (UV-Vis) and Raman spectroscopy. It was proposed that carbon onions could be a possible carrier of the 2175 A interstellar absorption bump. ° Raman spectra of this material revealed pronounced differences to other graphitic materials. ... 

Optical Properties of Carbon Onions 10.4.2.1 Transmittance and Absorption... 

Since the discovery of carbon onions, it has been believed that they are a component of the interstellar dust and that they contribute to the strong absorption band centered at a wavelength of 217.5 nm.23 3o. ). 7,88 Optical transmission spectroscopy measurements in the wavelength range of... 

Henrard, L., Lambin, P.H., Lucas, A. A., 1997, Carbon onions as possible carriers of the 2175 Angstrom interstellar absorption bump, Astrophysics. J. 487, 719-727. 

Tomita, S., Hayashi, S., Tsukuda, Y, Fujii, M., 2002b, Ultraviolet-visible absorption spectroscopy of carbon onions, Phys. Solid State 44,450-453. 

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