Fulleranes and Carbon Nanostructures in the Interstellar Medium

Abstract We review the potential contribution of single fullerenes and buckyonions to interstellar extinction. Photoabsorption spectra of these molecules are compared with some of the most relevant features of interstellar extinction, the UV bump, the far UV rise and the diffuse interstellar bands. According to semiempirical models, photoabsorption by fullerenes (single and multishell) could explain the shape, width and peak energy of the most prominent feature of the interstellar absorption, the UV bump at 2,175 A. Other weaker transitions are predicted in the optical and near-infrared providing a potential explanation for diffuse interstellar bands. In particular, several fullerenes could contribute to the well known strong DIB at 4,430 A comparing cross sections and available data for this DIB and the UV bump we estimate a density of fullerenes in the diffuse interstellar medium of 0.1-0.2 ppm. These molecules could then be a major reservoir for interstellar carbon. 

We give an estimation of the carbon fraction locked in these molecules. We discuss the rotation rates and electric dipole emission of hydrogenated icosahedral fullerenes in various phases of the interstellar medium. These molecules could be the carriers of the anomalous microwave emission detected by Watson et al. (Astrophys. J. 624 L89,2005) in the Perseus molecular complex and Cassasus et al. (2006) in the dark cloud LDN 1622. Hydrogenated forms of fullerenes may account for the dust-correlated microwave emission detected in our Galaxy by Cosmic Microwave Background experiments. 

1 Institute de Astrofisica de Canarias, 38200 La Laguna, Tenerife, Spain e-mail sigroth iac.es 

2Istituto Nazionale di Astrofisica di Catania, 95123 Catania, Italy Actinium Chemical Research, 00133 Rome, Italy e-mail franco.cataldo fastwebnet.it 

Cataldo and S. Iglesias-Groth (eds.), Fulleranes The Hydrogenated Fullerenes, Carbon Materials Chemistry and Physics 2, DOI 10.1007/978-l-4020-9887-l l, Springer Science+Business Media B.V. 2010 

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