Strong-field ionization of molecules by few-cycle pulses

Abstract

Few-cycle pulses of 800 nm light cause ionization and dissociation of triatomic molecules like H₂O and CS₂ in the temporal regime where only electron rescattering dominates the laser-molecule interaction. In case of ionization of H₂O, significantly higher amounts of kinetic energy are released upon dissociation into atomic fragments. However, the case of CS₂ is somewhat special in that the wave packet of the rescattered electron destructively interferes with the antibonding p orbital of CS₂⁺ such that rescattering is also essentially turned off. Under such circumstances the dissociation channel is absent and long-lived singly, doubly, and triply charged molecular ions dominate the mass spectrum in the few-cycle regime. This brings to the fore the importance of molecular symmetry in strong-field ionization. Ultrafast atomic rearrangements are also observed: H atoms in H₂O are rearranged by strong optical fields generated by intense 9.3 fs laser pulses to form a new bond leading to H₂⁺; experiments show that this bond formation occurs within a single laser pulse.