Energy Transfer in Charge Exchange Collisions between Slow Ions and Rydberg Atoms

Charge transfer collisions between slow ions and Rydberg atoms have been studied for ion charges q0ex0ex=0ex0ex1--4, using resonant laser excitation to detect specific energy states of the collision products. The data collected show a clear resonance in the capture cross section to a particular energy state as the binding energy of the Rydberg target is varied. The resonance position differs significantly from the predictions of the classical overbarrier model, and its width becomes very small (0.025 eV) at the lowest velocities studied.