Vibrationally resolved structure in O_2~+ dissociation induced by intense ultrashort laser pulses

摘要

Laser-induced dissociation of O_2~+ 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, ～10~(15) W/cm~2). The measured kinetic energy release spectra from dissociation of O_2~+ and dissociative ionization of O_2 reveal vibrational structure which persists over a wide range of laser intensities. The vibrational structure is similar for O_2~+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~4n_u state via the dissociation pathway |a~4n_u >→f~4n_g-1_ω)-a mechanism equivalent to bond softening in H_2~+ .