  Optimal control techniques combined with femtosecond laser pulse shaping are
applied to steer and enhance the strong-field induced emission of highly
charged atomic ions from silver clusters embedded in helium nanodroplets. With
light fields shaped in amplitude and phase we observe a substantial increase of
the Ag$^{q+}$ yield for $q>10$ when compared to bandwidth-limited and optimally
stretched pulses. A remarkably simple double-pulse structure, containing a
low-intensity prepulse and a stronger main pulse, turns out to produce the
highest atomic charge states up to Ag$^{20+}$. A negative chirp during the main
pulse hints at dynamic frequency locking to the cluster plasmon. A numerical
optimal control study on pure silver clusters with a nanoplasma model converges
to a similar pulse structure and corroborates, that the optimal light field
adapts to the resonant excitation of cluster surface plasmons for efficient
ionization.
