The resonant charge hopping rate in positively charged helium clusters

We have calculated the cluster size dependence of the time and distance scales for positive charge migration via resonant charge transfer in helium clusters. The calculation employs the Born-Oppenheimer approximation and the approximation that pairs of helium atoms interact independently. The splitting of the (2) Sigma(u)(+)-(2) Sigma(g)(+) valence potential curves for He-2(+) was averaged over the pair distribution functions for He-n, clusters with 20 less than or equal to n less than or equal to 200. The mean time between hops decreases slowly with cluster size from 35 fs for 20-atom clusters to 19 fs for 200-atom clusters. The mean hopping distance is 3.1 Angstrom, independent of cluster size. (C) 1998 Elsevier Science B.V.