Temperature dependent solvation dynamics of electrons after one-photon detachment in aqueous iodide

The electron photodetachment from 2.5 mM aqueous iodide solution is studied in the temperature range 25 to 75°C. The dynamics following excitation of the anion at 242 nm into the lowest CTTS state are studied in the spectral range of 400-1000 nm. A first intermediate is observed that builds up with a time constant of 220 to 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. The latter builds up with a time constant of 700 to 540 fs going from 25°C to 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. The experimental result for the lifetime of the hydrated I:e ^- pair is 21 to 16 ps going from 25°C to 757deg;C.