Strong-field ionization of water by intense few-cycle laser pulses

Ionization of H₂O is caused by four-cycle pulses of intense 800-nm light in the temporal regime where processes like enhanced ionization and spatial alignment are “switched off” and recollision dominates the laser-molecule interaction. Nonadiabatic effects drive the overall dynamics in the few-cycle regime and give rise to multiple ionization of the molecule to electronically excited ionic states. The direct experimental manifestation of such nonadiabatic effects is in significantly higher amounts of kinetic energy being released upon dissociation into atomic fragments. The energy spectrum of H⁺ fragments enables us to deduce that recollision of the optical-field-ejected electron with the molecular ion drives the overall dynamics.