THE CHEMISTRY OF SILICON IN HOT MOLECULAR CORES

The gas-phase chemistry of hot molecular cores is thought to depend upon the composition of evaporated ice mantle material and its subsequent gas-phase reactions. Hydrogenated species are thought to predominate within the ices. Since monosilane, SiH4, is the likely reservoir for silicon, we have modelled its influence upon hot core chemistry. For a range of likely temperatures and densities, we find that its evaporation results in substantial fractional abundances of SiO, along with H2SiO and HNSi in a time-scale of a few x 10(4) yr, while itself remaining the major gas-phase silicon species. In the absence of available molecular oxygen, atomic silicon and carbon-silicon species such as HCSi and SiCH2 are shown to become increasingly abundant.