Time-resolved inner-shell photoelectron spectroscopy : From a bound molecule to an isolated atom

Due to its element and site specificity, inner-shell photoelectron spectroscopyis a widely used technique to probe the chemical structure of matter. Here, we show that time- resolvedinner-shell photoelectron spectroscopycan be employed to observe ultrafast chemical reactions and the electronic response to the nuclear motion with high sensitivity. The ultraviolet dissociation of iodomethane (CH3I) is investigated by ionization above the iodine 4d edge, using time- resolvedinner-shell photoelectron and photoion spectroscopy. The dynamics observed in the photoelectron spectra appear earlier and are faster than those seen in the iodine fragments. The experimental results are interpreted using crystal-field and spin-orbit configuration interactioncalculations, and demonstrate that time- resolvedinner-shell photoelectron spectroscopyis a powerful tool to directly track ultrafast structural and electronic transformations in gas-phase molecules.