Suppression of Multiple Ionization of Atomic Ions in Intense Ultrafast Laser Pulses

The interaction of an intense laser field with a beam of atomic ions has been investigated experimentally for the first time. The ionization dynamics of ${\mathrm{Ar}}^{+}$ ions and Ar neutrals in a 60 fs, 790 nm laser pulse have been compared and contrasted at intensities up to ${10}^{16}\mathrm{W}{\mathrm{cm}}^{-2\mathrm{}}$. Our results show that nonsequential ionization from an ${\mathrm{Ar}}^{+}$ target is strongly suppressed compared with that from the corresponding neutral target. We have also observed for the first time the strong field ionization of high lying target metastable levels in the ${\mathrm{Ar}}^{+}$ beam.