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000002209 005__ 20160701171701.0
000002209 0247_ $$2DOI$$a10.1088/0004-637X/757/1/41
000002209 037__ $$aASTROimport-366
000002209 100__ $$aBernard-Salas, J.
000002209 245__ $$aOn the Excitation and Formation of Circumstellar Fullerenes
000002209 260__ $$c2012
000002209 520__ $$aWe compare and analyze the Spitzer mid-infrared spectrum of three fullerene-rich planetary nebulae in the Milky Way and the Magellanic Clouds: Tc1, SMP SMC 16, and SMP LMC 56. The three planetary nebulae share many spectroscopic similarities. The strongest circumstellar emission bands correspond to the infrared active vibrational modes of the fullerene species C60 and little or no emission is present from polycyclic aromatic hydrocarbons. The strengths of the fullerene bands in the three planetary nebulae are very similar, while the ratios of the [Ne III]15.5 µm/[Ne II]12.8 µm fine structure lines, an indicator of the strength of the radiation field, are markedly different. This raises questions about their excitation mechanism and we compare the fullerene emission to fluorescent and thermal models. In addition, the spectra show other interesting and common features, most notably in the 6-9 µm region, where a broad plateau with substructure dominates the emission. These features have previously been associated with mixtures of aromatic/aliphatic hydrocarbon solids. We hypothesize on the origin of this band, which is likely related to the fullerene formation mechanism, and compare it with modeled hydrogenated amorphous carbon that present emission in this region. 
000002209 700__ $$a Cami, J.
000002209 700__ $$a Peeters, E.
000002209 700__ $$a Jones, A. P.
000002209 700__ $$a Micelotta, E. R.
000002209 700__ $$a Groenewegen, M. A. T.
000002209 773__ $$c41$$i1$$pThe Astrophysical Journal$$v757$$y2012
000002209 85642 $$ahttp://esoads.eso.org/abs/2012ApJ...757...41B
000002209 905__ $$apublished in
000002209 980__ $$aREFERD