Femtosecond studies of electron photodetachment from an iodide ion in solution: The trapped electron

We have performed femtosecond studies of electron photodetachment from a simple halide ion in aqueous solution. After photoexcitation, the electron is trapped in the deep potential well formed by the orientational polarization of the water molecules around the anion. This trapped state of the electron is a precursor of the wet electron and in the case of an aqueous iodide ion has a strong absorption in the visible. We hypothesize that the electron recombines with the neutral halogen atom or crosses onto the potential surface of the wet electron by a non-adiabatic electron transfer process. We find that analogous to the case of photoionization of a neutral water molecule, the wet to solvated electron transition in the vicinity of the halogen atom can be described as two-state in character.