Picosecond recombination dynamics of electrons in ionic liquids.

We report picosecond transient optical absorption decays for electrons localized in F-center analogues in molten KCl and KBr. The absorption decays extend to 750 ps after excitation by a 266 nm ultraviolet pulse. The recombination process is analyzed in terms of reactions involving the anionic hole centers X sub 2 bar and X sub 3 bar where X = Cl or Br. The results confirm by direct real-time measurement that F-center electrons are sufficiently mobile to account for the observed electronic conductivity in dilute metal-molten salt solutions. This demonstrates the necessary presence of a polaron-like transport mechanism.