Electron Localization in Hydrogen

Abstract

The control of the electronic motion inside a molecule by a light pulse is an ambitious goal with important implications for the steering in real time of the outcome of a chemical reaction. In femtochemistry, the unfolding of a reaction (for example the dissociation of a bound molecule) can be controlled by applying a femtosecond pulse whose envelope and frequency variations can be controlled and modified by using well established pulse shaping techniques. Technological breakthroughs over the last years have made available a new strategy for steering the dynamics of a bound electron wave packet based on the precise control of the electric field waveform rather than of its instantaneous frequency. In particular few-cycle pulses with a reproducible electric field have been demonstrated and applied to different strong field experiments and, in particular, to the generation of isolated attosecond pulses, which can trigger a reaction on a timescale shorter or comparable to the typical timescale of the electronic dynamics. The combination of field controlled few femtosecond pulses and attosecond XUV light bursts allows one to control with unprecedented temporal resolution the unfolding of ultrafast dynamics occurring in small molecules. As examples, we will review few experiments performed in hydrogen and deuterium based on single (intense IR few-cycle pulse) or two pulses (intense IR few-cycle pulses and isolated or train of attosecond pulses) in which the control of the electron localization during the dissociation of the molecular ion ($\mathrm{H}_{2}^{+} /\mathrm{D}_{2}^{+}$) was achieved. The experiments show that different mechanisms can be involved in the localization process unveiling the rich attosecond and femtosecond dynamics occurring in light molecules.