Abstract
The equilibrium chemistry of silicon in dense interstellar clouds is discussed in terms of both gas phase and grain surface reactions. Unless the metal depletion is very large, the gas phase scheme tends to over-produce SiO and/or SiS when compared to the observations of Sgr B2. The scheme also predicts SiC to be an abundant form of silicon. There is a great need for relevant laboratory data on the reactions used here—of the 35 rate coefficients adopted in the scheme, only three have been measured in the laboratory. Reactions between positively charged gas phase ions and small grains can lead to the formation of SiO and SiS. This type of reaction seems to offer a simple explanation for the observed differences between sulphur and silicon chemistry in dense clouds.
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Millar, T.J. Silicon chemistry in dense clouds. Astrophys Space Sci 72, 509–517 (1980). https://doi.org/10.1007/BF00639153
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DOI: https://doi.org/10.1007/BF00639153