Observation of Cold Collisions between Trapped Ions and Trapped Atoms. A. Grier, M. Cetina, F. Orucevic, and V. Vuletic, Phys. Rev. Lett. 102, 223201 (2009).
Figure - Trapped Yb+ ion crystal (left a,b) and overlapped Yb MOT cloud (left c,d) imaged along two different directions. The figure on the right shows the measured rate coefficient for Yb++Yb charge exchange collisions, the solid line indicates the expected value for a Langevin process. Note the logarithmic collision energy axis: the rate coefficient is constant over three orders of magnitude in collision energy.
We have studied 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 (kB × 35 mK). The minimum measured rate coefficient of 6×10-10 cm3 s-1 is in good agreement with that derived from a Langevin model for an atomic polarizability of 143 a.u.