Accurate quantum mechanical rate constants (all contributing partial waves, fine energy grid Boltzmann averaging) for the title reaction are obtained by the hyperquantization algorithm, covering the range from above room temperature down to the cold regime (few K). The good agreement with available experiments down to similar to200 K, obtained by blending ab initio description of the transition state and molecular beam scattering experimental characterization of the entrance channel, establishes the reliability of the approach to describe deviations from Arrhenius behavior at those low temperatures where quantum mechanics can induce specific selectivity in chemical reactivity (C) 2003 Elsevier Science B.V. All rights reserved.