Non-sequential double ionization of atoms with phase-controlled ultra-short laser pulses

Abstract

This thesis reports about experimental studies of the non-sequential double ionization of atoms. This mechanism, where an ionized electron, driven by the laser electric field, recollides to further ionize the ion, is investigated using light pulses containing only a few optical cycles. They permit to restrict the interaction time between the laser electric field and the system. The carrier-envelope phase, defining the field-specific shape, is experimentally characterized for every pulse. The coincident detection of the produced ions and electrons is performed using a Reaction Microscope allowing measuring the threedimensional momentum of each charged particle. The information about the correlated dynamics of the two ionized electrons is extracted. We examine the influence the ionized targets - argon and neon - and the intensity have on these correlations. For argon, by decreasing the intensity of the laser pulses and therefore the electron impact energy, a doubly excited state of the system is formed after recollision. This mechanism is confirmed by semi-classical simulations reproducing the characteristics of our experimental system. Properties of this transition state - such as its decay time - are shown to be strongly correlated to the measured electron momentum. Finally, another experimental realization enabling to control the recolliding electron trajectories is presented.