February 2005

Silicon Dicarbide

The breakthrough that led to the discovery of silicon dicarbide (c-SiC2) by Thaddeus et al. in 1984 was laboratory work of Michalopoulos et al. which demonstrated that it has a cyclic rather than a linear structure, as previously assumed. The species was observed toward IRC +10216, in the circumstellar shell where a large number of astromolecules have been first identified. Additional rotational lines associated with heavier Si isotopes (masses 29 and 30) were subsequently reported by Cernicharo et al.

The earliest observation of SiC2 was not in the interstellar or circumstellar media but in the stellar atmospheres of N class stars. These are carbon stars that fall at the cool end of the spectral range.

Silicon dicarbide is one of several known astromolecules with a three-membered ring cyclic structure. These also include 2-cyclopropyn-1-yl (c-C3H), cyclopropenylidene (c-C3H2), ethylene oxide (c-C2H4O), and cyclopropenone (c-H2C3O). Additional information about the spectroscopy of SiC2 from Michael Geusic's thesis can be found here.


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