Solvent-Mediated Electron Hopping: Long-Range Charge Transfer In IBr(CO2) Photodissociation

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Science  04 Mar 2010:
DOI: 10.1126/science.1184616


Chemical bond breaking involves coupled electronic and nuclear dynamics that can take place on multiple electronic surfaces. Here, we report a time-resolved experimental and theoretical investigation of nonadiabatic dynamics during photodissociation of IBr(CO2) excited to the A′ electronic state. Previous experimental work showed that dissociation of bare IBr yields only I + Br products. However, in IBr(CO2), time-resolved photoelectron spectroscopy reveals that a subset of the dissociating molecules undergo an electron transfer from iodine to bromine 350 fs after the initial excitation. Ab initio calculations and molecular dynamics simulations elucidate the mechanism for this charge hop and highlight the crucial role of the CO2 molecule. The charge transfer between two recoiling atoms, assisted by a single solvent-like molecule, provides a remarkable limiting case of solvent-driven electron transfer over a distance of 7 Å.