We report experiments where hydrogen molecules were dissociatively ionized by an attosecond pulse train in the presence of a near-infrared field. Fragment ion yields from distinguishable ionization channels oscillate with a period that is half the optical cycle of the IR field. For molecules aligned parallel to the laser polarization axis, the oscillations are reproduced in two-electron quantum simulations, and can be explained in terms of an interference between ionization pathways that involve different harmonic orders and a laser-induced coupling between the 1sσg and 2pσu states of the molecular ion. This leads to a situation where the ionization probability is sensitive to the instantaneous polarization of the molecule by the IR electric field and demonstrates that we have probed the IR-induced electron dynamics with attosecond pulses.

Phys. Rev. Lett.

Kelkensberg, F., Siu, W., Pérez-Torres, J. F., Morales, F., Gademann, G., Rouzée, A., … Vrakking, M. J. J. (2011). Attosecond control in photoionization of hydrogen molecules. Phys.Rev.Lett., 107(4, Article number: 43002), 1–4. doi:10.1103/PhysRevLett.107.043002