Due to an error in the preparation of the manuscript, the solutions of Eqs.(2) and (3), reported in the paper and used in the data fitting, are not correct. We report the correct fitting functions and the revised results of the time resolved data. The error removal leads to a decrease of the Förster radius extracted from the time resolved PL from R 0= 80±15 Å to R 0= 48±3 Å, which is closer to the one extracted from the spectra (R 0= 56±2 Å), thus strengthening the general conclusions of the paper. The best fit acceptor decay time is also reduced from about τ A= 220±10 ps to τ A= 145±10 ps.