  The laser intensity dependence of the recoil energies from the Coulomb
explosion of small argon clusters has been investigated by resolving the
contributions of the individual charge states to the ion recoil energy spectra.
Between $10^{14}$ and $10^{15}$ W/cm$^2$ the high-energy tail of the ion energy
spectra changes its shape and develops into the well-known knee feature, which
results from the cluster size distribution, laser focal averaging, and
ionization saturation. Resolving the contributions of the different charge
states to the recoil energies, the experimental data reveal that the basic
assumption of an exploding homogeneously charged sphere cannot be maintained in
general. In fact, the energy spectra of the high-$q$ show distinct gaps in the
yields at low kinetic energies, which hints at more complex radial ion charge
distributions developing during the laser pulse impact.
