Electron Rearrangement Dynamics in DissociatingI2n+Molecules Accessed by Extreme Ultraviolet Pump-Probe Experiments

The charge rearrangement in dissociating ${\mathrm{I}}_{2}^{n+}$ molecules is measured as a function of the internuclear distance $R$ using extreme ultraviolet pulses delivered by the free-electron laser in Hamburg. Within an extreme ultraviolet pump-probe scheme, the first pulse initiates dissociation by multiply ionizing ${\mathrm{I}}_{2}$, and the delayed probe pulse further ionizes one of the two fragments at a given time, thus triggering charge rearrangement at a well-defined $R$. The electron transfer between the fragments is monitored by analyzing the delay-dependent ion kinetic energies and charge states. The experimental results are in very good agreement with predictions of the classical over-the-barrier model demonstrating its validity in a thus far unexplored quasimolecular regime relevant for free-electron laser, plasma, and chemistry applications.