Recombination by Electron Capture in the Interstellar Medium

Rate constants for charge transfer processes in the interstellar medium are calculated using ab-initio molecular calculations. Two important reactions are presented: the recombination of Si2+ and Si3+ ions with atomic hydrogen and helium which is critical in determining the fractional abundances of silicon ions, and the C+ + S -> C+ S+ reaction, fundamental in both carbon and sulphur chemistry.