Measurements of the Reaction Rate Coefficients of Atomic Hydrogen with Astrochemical Anions: CN− and C3N−

We present the temperature-dependent reaction rate coefficients of CN− and C3N− with atomic hydrogen in the temperature range from 7 to 290 K, measured in a 16-pole radio-frequency ion trap. The rate of C3N− with H steadily increases toward lower temperatures, while the rate coefficients for the CN− + H system show a sudden change around 160 K. Fits to the data were performed to determine temperature-dependent reaction rate coefficients. The fits reveal a rate coefficient of cm3 s−1 for C3N− + H. For CN−, we determined a rate coefficient for the temperature regime below 160 K of cm3 s−1. Given our present results, higher rate coefficients than previously reported must be assumed for the modeling of cold interstellar environments involving these H atom reactions.