Ultrafast spectroscopy of the aqueous chloride ion: A quantum molecular dynamics study

The photodetachment dynamics of an electron from a chloride ion in water induced by the excitation of the lowest charge-transfer-to-solvent state is studied by means of quantum molecular dynamics simulations. On a subpicosecond time scale, the dominant reaction mechanism is the formation of a stable electron-atom pair. The transient absorption spectra characterizing the formation of the pair are explored. A theoretical expression of the signal in terms of a few easily computable statistical quantities is proposed, which allows for a quantitative comparison between the simulation results and the experimental spectra of Gauduel et al. [Chem. Phys. 197, 167 (1995)]. The observed transient absorption is explained in terms of a solvent-driven frequency shift mecanism.