Temperature-Dependent Reaction Kinetics of the Carbanions C and CH ( = 2 and 4) with H Atoms in a Cryogenic Ion Trap.

We report on the temperature-dependent reactions of the carbon-chain anions C and C, as well as the hydrocarbons CH and CH 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 C, C, and CH anions, the values are about a factor of 2 smaller than the Langevin capture rate coefficient, while for CH, 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.