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

We studied the nuclear dynamics of diatomic molecular ions in intense infrared laser fields by analyzing their fragment kinetic energy release (KER) spectra as a function of time [1]. We found that, in general, ionization of the neutral parent molecule by an ultra-short pump pulse populates several intermediate electronic states of the molecular ion that contribute to the same KER. Within the Born-Oppenheimer (BO) approximation, we calculated \textit{ab--initio} adiabatic potential energy curves for the molecular ions and their electric dipole-couplings, using the quantum chemistry code GAMESS [2]. By comparing KER spectra that result from the nuclear dynamics on individual and on dipole coupled BO potential curves with that measured for O$_{2}$ molecules, we developed a scheme for identifying intermediate states of the molecular ions that are relevant during the dissociation dynamics. \\[4pt] [1] S. De \textit{et al}., PRA \textbf{80}, 011404 (2009); S. De \textit{et al}, PRA \textbf{84}, 043410 (2011) \\[0pt] [2] M. W. Schmidt \textit{et al}, J. Comput. Chem., \textbf{14}, 1347 (1993).