Interstellar carbon chemistry: Reaction rates of neutral atomic carbon with organic molecules

Experimentally measured rate constants for the chemical reactions of ground state carbon atoms with several alkenes and alkynes are found to have surprisingly large values (approximately 10-10 - 10-9/cu cm molecule/s). The rate constants increase significantly with the size of the molecule. The experimental results agree well with a simple classical capture theory which predicts a dependence of the rate constant on N1/3, where N is the number of carbon atoms in the molecule. The results suggest that the reactions of ground state carbon atoms with organic molecules should be included in the chemical reaction networks used to model interstellar clouds.