Experimental Separation of Sub-Cycle Ionization Bursts in Strong-Field Double Ionization of H${}_2$

We report on the unambiguous observation of the sub-cycle ionization bursts in sequential strong-field double ionization of H${}_2$ and their disentanglement in molecular frame photoelectron angular distributions. This observation was made possible by the use of few-cycle laser pulses with a known carrier-envelope phase in combination with multi-particle coincidence momentum imaging. The approach demonstrated here will allow sampling of the intramolecular electron dynamics and the investigation of charge-state specific Coulomb-distortions on emitted electrons in polyatomic molecules.