Charge State Dependent Energy Loss of Slow Heavy Ions in Solids

The loss of kinetic energy of slow $\left({v=0.3v}_{\mathrm{Bohr}}\right)$ ions transmitted through thin carbon foils has been measured as a function of projectile charge state in the range from $q=3+$ for oxygen to $q=69+$ for gold ions. For the first time, charge state dependent energy loss enhancements have been observed for ${\mathrm{Xe}}^{q+}$ and ${\mathrm{Au}}^{q+}$ at $q\ge 40+$, indicating strong preequilibrium contributions to the energy loss of slow, highly charged ions in solids.