Towards attosecond - observation of electron tunnelling

Atoms become ions when exposed to extremely intense light. The process is predicted to occur via tunnelling through the binding potential that is suppressed by the light field near the peaks of its oscillations. Professor F. Krausz (Max Planck Institute of Quantum Optics in Garching, Germany) and his collaborators recently reported the real-time observation of this most elementary step in strong-field interactions, i.e., light-induced electron tunnelling. The team used 250-attosecond pulses of UV radiation, and confirmed theoretical predictions about the tunneling process. It was also found that the process lasted for several hundred attoseconds, depleting atomic-bound states. This would suggest that the use of tunneling itself is feasible for probing short-lived, transient states of atoms or molecules, e.g., multi-electron excitation (shake-up) and relaxation (cascaded Auger decay) processes etc. For more information, see the paper, "Attosecond real-time observation of electron tunnelling in atoms", M. Uiberacker et al., Nature, 446, 627 (2007).