Reaction of an Ion and a Free Radical near 0 K: He + NO → He + N + O.

The reactions between ions and free radicals are among the fastest chemical reactions. They are predicted to proceed with large rates, even near 0 K, but so far, this prediction has not been verified experimentally. We report on measurements of the rate coefficient of the reaction between the ion He and the free radical NO at collision energies in the range between 0 and ∼ ·10 K.