Dissociation dynamics of O$_{2}^{+}$ in intense laser fields

We investigated the nuclear dynamics of the electronically and vibrationally excited O$_{2}^{+}$ molecules by applying intense ultrashort IR probe pulses and measuring the fragment kinetic energy release (KER) spectra as a function of the pump-probe delay. To analyze these spectra, we performed vibrational-wave-packet-propagation calculations on adiabatic O$_{2}^{+}$ potential curves. First, to identify relevant transiently populated electronic states of O$_{2}^{+}$, we modeled the pump step in Franck-Condon approximation and calculated the time evolution of initial O$_{2}^{+}$ vibrational wave packets separately for selected molecular potential curves. The comparison of calculated KER spectra as a function of delay, quantum beat frequency, and vibrational revival times for one adiabatic curve at a time with experimental spectra serves as a guide for selection of relevant O$_{2}^{+}$ electronic states. Next, we included probe-laser-induced dipole couplings between the relevant molecular potential curves and compared the improved calculated KER spectra with the experiment, in an attempt to reveal non-adiabatic effects in measured KER spectra that are due to the coupled motion of vibrational wave packets in different electronic states.