“…As discussed in Ref. 5, the tunneling effect is mainly determined by the imaginary frequency i and is adequately described by the Wigner tunneling theory. 12 According to this theory, the ratio between the rate constants with and without tunneling is given by the tunneling factor =1+ For example, at room temperature ͑300 K͒, the tunneling factors are 1.16 and 1.22 for the frozen and relaxed surface models, respectively.…”