Crossed molecular beam studies of some ion molecule reactions of C+ and CH3+

The astrophysically important ion-molecule condensation reactions of C+ and CH3+ with C2H2 and C2H4 as well as those of C+ with H2O, O2, and HCl were investigated by the crossed molecular beam method over the energy range 0.5-2.0 eV. Reactant ion beams were generated by dissociative charge transfer or by electron impact while neutral beams were generated by a supersonic nozzle expansion of the neat gases or of seeded mixtures with H2. Energy and angular distributions of the products were obtained and transformed to center of mass (CM) relative doubly differential cross sections. The condensation reactions with C2H2 and C2H4 were found to proceed via an osculating mechanism as indicated by the symmetry of the CM angular distributions at the low end of the energy range and by their shift to the forward direction at higher energies. The reactions of C+ with H2O and O2 were found to proceed through long-lived collision complexes with lifetimes on the order of 1 psec. All the condensation reactions yielded highly internally excited products having nonstatistical relative recoil energy distributions as compared to theoretically calculated statistical distributions. The decarbonylation of acetaldehyde by Fe+ at 0.5 eV and by Cr+ at 1.0 eV relative energies was also studied by the crossed beam method