Clocking Dissociative Above-Threshold Double Ionization of H2 in a Multicycle Laser Pulse

Abstract

The dissociative above-threshold double ionization (ATDI) of ${\mathrm{H}}_2$ in strong laser fields involves the sequential releasing of two electrons at specific instants with the stretching of the molecular bond. By mapping the releasing instants of two electrons to their emission directions in a multicycle polarization-skewed femtosecond laser pulse, we experimentally clock the dissociative ATDI of ${\mathrm{H}}_2$ via distinct photon-number-resolved pathways, which are distinguished in the kinetic energy release spectrum of two protons measured in coincidence. The timings of the experimentally resolved dissociative ATDI pathways are in good accordance with the classical predictions. Our results verify the multiphoton scenario of the dissociative ATDI of ${\mathrm{H}}_2$ in both time and energy fashion, strengthening the understanding of the strong-field phenomenon and providing a robust tool with a subcycle time resolution to clock abundant ultrafast dynamics of molecules.