Single-Cycle Non-Sequential Double Ionization

Non-sequential double ionization (NSDI) is a process in which two electrons are ripped off an atom or molecule by a strong laser field in a correlated manner. Although NSDI has been the subject of numerous experimental and theoretical studies over the past three decades, the exact mechanisms responsible for the observed energy and momentum sharing between the electrons generated in the process, are not yet fully understood. The main reason lies in the fact that the theoretical description of the complex correlated many body dynamics that govern NSDI is exceedingly difficult. A particularly challenging task for theory is the modeling of NSDI dynamics over time scales exceeding one period of the laser field. As a result, most calculations are restricted to a single laser cycle. On the experimental side, in contrast, kinematically complete experiments on single-cycle NSDI has long been prohibitively challenging. Therefore, the comparison between theory and experiments has been limited, so far, to a very qualitative level. We review recent results obtained from first kinematically complete NSDI experiments in the single cycle regime. We illustrate the insight gained from these experiments, and discuss how the new experimental data may facilitate verification of theoretical models on a quantitative level.