Vibrationally resolved structure in O2+ dissociation induced by intense ultrashort laser pulses

Laser-induced dissociation of O2+ is studied in the strong-field limit using two independent methods, namely a crossed laser-ion-beam coincidence 3D momentum imaging method and a supersonic gas jet velocity map imaging technique (790 and 395 nm, 8-40 fs, ∼1015 W/cm2). The measured kinetic energy release spectra from dissociation of O2+ and dissociative ionization of O2 reveal vibrational structure which persists over a wide range of laser intensities. The vibrational structure is similar for O2+ produced incoherently in an ion source and coherently by laser pulses. By evaluation of the potential energy curves, we assign the spectral energy peaks to dissociation of the v=10-15 vibrational states of the metastable a 4Πu state via the dissociation pathway |a 4Πu>→|f 4Πg-1ω>--a mechanism equivalent to bond softening in H2+.