Charge Equilibration Time of Slow, Highly Charged Ions in Solids

We report observations of nonequilibrium charge state distributions of slow, highly charged (33+≤q≤75+) ions after transmission of thin carbon foils. Charge equilibration times are determined directly from the dependencies of exit charge states on projectile velocity (0.5×10⁶<v<10⁶m/s) and foil thickness (5--10 nm). Ions like Xe⁴⁴⁺ and Au⁶⁸⁺ are found to equilibrate inside of solid matter in a time of only 7 fs.