Dynamic control of the fragmentation of CO$^{q+}$ excited states generated by high order harmonics*

The dynamic process of fragmentation of CO$^{q+ }$is investigated by using an EUV pump pulse (35-42eV) generated by high-order harmonics. A time-delayed infrared (IR) probe pulse is used to interact with the excited system and trace the wave-packet evolution. The experimental results indicate that two groups of states prepared by the EUV contribute to C$^{+}$-O$^{+}$ fragmentation: (a) a double ionization with a kinetic energy release (KER) above 6eV and (b) a fragmentation of the cation into C$^{+}$-O*, followed by autoionization of the O*. Channel (b) has a KER near 3eV in the absence of IR, increasing to more than 6eV in the presence of IR. This KER increase drops off with EUV/IR time delay and has a lifetime of $\sim $250 fs. A model TDSE solution gives qualitative agreement with experiment.