Non-sequential double ionization in slow charge fragmentation of doubly ionized NO

With ultrahigh time-resolution time-of-flight measurements, we identify a new N⁺ + O⁺ dissociation channel following doubly ionized NO. This dissociation channel has a relatively small kinetic energy release. A relatively high non-sequential double ionization rate is found to exist in this N⁺ + O⁺ channel for linear polarization, but non-sequential double ionization nearly vanishes for circular polarization. These results corroborate the understanding that electronic structures play a key role in influencing non-sequential double ionization in molecules.