Earth Planets Space, Vol. 65 (No. 10), pp. 1069-1081, 2013
Yong Zhang and Sun Kwok
Department of Physics, University of Hong Kong, Pokfulam, Hong Kong, China
(Received October 31, 2012; Revised May 20, 2013; Accepted June 18, 2013; Online published October 24, 2013)
C60 (buckminsterfullerene) was recently discovered in a variety of circumstellar environments by the Spitzer Space Telescope, suggesting that the envelopes
around evolved stars are active sites for the synthesis of fullerenes. However, the physical state, excitation mechanism, and formation route of circumstellar C60 are not completely understood so far. These open issues are discussed in this paper. For that purpose we investigate the observed wavelengths and
strengths of C60 bands and compare them with the experimental values. We
also statistically study the environments and emission properties of the C60 sources. We would like to stress that improved flux measurements and more accurate Einstein coefficients are required to draw solid conclusions. Furthermore, we present possible detections of hydrogenated C60 and C60+, and discuss their implications on fullerene chemistry in circumstellar environments.
Key words: Infrared, ISM, AGB and post-AGB, circumstellar matter, molecules.