Photodetachment of aqueous iodide: Variation of the excitation energy and solution temperature

This chapter presents a report on the photodetachment of electrons in a 2.5 mM aqueous iodide solution at temperature values of 25, 50, and 75°C. After one-photon excitation by a 100 femtosecond (fs)-pulse at 242 nm, the dynamics are studied with 100 fs probe radiation in the spectral range of 400-1100 nm. The initially excited lowest charge transfer state shows a broad excited-state absorption in the NIR with a maximum around 1000 nm. The excess electron escapes the anion solvation shell within 200 fs. The further separation of the electron from the iodine atom and the assembling of a new solvation configuration around the atom-electron pair require 700 to 540 fs. This process is accounted for by equilibration of the intermediate. The subsequent slower dynamics indicated by an absorption decrease are found to be strongly temperature dependent and explained by a competition of pair dissociation and geminate recombination. The relaxation dynamics are described by the diffusion of the particles in thepresence of an attractive interaction potential with depth of 850 + 100 cm.