Femtosecond dynamics of electron photodetachment of the fluoride anion in liquid water

The photoionization dynamics of aqueous fluoride after two-photon excitation at 310.5 nm is studied by pump-probe absorption spectroscopy. The initial population of the CTTS band is found to decay with a time constant of 380 fs to the lowest s-like charge transfer level. Out of this state with a lifetime of 430 fs, a rather long-lived atom-electron-water complex, (F:e ^-)_solv is formed. The quantum yield of the process is strongly suggested to be reduced by internal conversion to the fluoride ground level, η_pair∼0.5 to 0.7. Electron detachment to the final solvated electron competes with direct geminate recombination, so that 23% of the electrons return to the parent atom.