Observation of Cold Collisions between Trapped Ions and Trapped Atoms

We study cold collisions between trapped ions and trapped atoms in the semiclassical (Langevin) regime. Using Yb+ ions confined in a Paul trap and Yb atoms in a magneto-optical trap, we investigate charge-exchange collisions of several isotopes over three decades of collision energies down to 3 eV (kB35 mK). The minimum measured rate coefficient of 610-10 cm3 s-1 is in good agreement with that derived from a Langevin model for an atomic polarizability of 143 a.u.