Ion-recoil energy measurement in photoionization of laser-cooled rubidium

We report a measurement of the ion recoil energy in photoionization of laser-cooled atoms. ${}^{87}\mathrm{Rb},$ cooled in a magneto-optical trap, is two-photon ionized by a pulsed laser. The recoil energy is determined by time-of-flight in a weak electric field. A resolution in the range of 1 μeV is demonstrated. Refinement of the technique promises resolution in the range of several neV to be feasible.