Photoionization dynamics of an aqueous iodide solution: the temperature dependence

We report on the electron photodetachment dynamics after excitation at 242 nm of the lowest charge transfer state of aqueous I− at solution temperatures of 25, 50 and 75 °C. A first intermediate is observed that builds up with a time constant of 220-180 fs in the investigated temperature interval and is assigned to an iodine:electron pair in a transient solvent configuration. Subsequent solvent reorganization leads to a quasi-equilibrated hydrated atom:electron pair (I:e−)hyd that builds up with a time constant of 700-540 fs at 25-75 °C. The following relaxation seems to be governed by partially diffusion-controlled recombination of the electron in the presence of an attraction potential well with depth of about 850 cm−1.