Temperature-Dependent Reaction Kinetics of the Carbanions Cn–and CnH–(n= 2 and 4) with H Atoms in a Cryogenic Ion Trap

We report on the temperature-dependent reactions of the carbon-chain anions C2–and C4–, as well as the hydrocarbons C2H–and C4H–with H atoms in the temperature regime between 8 and 296 K. The experiments have been carried out in a temperature-variable radiofrequency multipole ion trap. From the measured kinetics, we have derived reaction rate coefficients that are constant for all considered systems in the measured temperature regime. For the C2–, C4–, and C4H–anions, the values are about a factor of 2 smaller than the Langevin capture rate coefficient, while for C2H–, the measured value agrees with the Langevin value. No theoretical calculations are available at present to explain this. All rate coefficients are in good agreement with previous measurements at room temperature.