Charge Equilibration Time of Slow, Highly Charged Ions in Solids

We report observations of nonequilibrium charge state distributions of slow, highly charged $(33+\le q\le 75+)$ ions after transmission of thin carbon foils. Charge equilibration times are determined directly from the dependencies of exit charge states on projectile velocity $(0.5\times {10}^6<v<\mathrm{}{10}^6\mathrm{m}/\mathrm{s})$ and foil thickness (5–10 nm). Ions like ${\mathrm{Xe}}^{44+}$ and ${\mathrm{Au}}^{68+}$ are found to equilibrate inside of solid matter in a time of only 7 fs.