We are developing an apparatus for investigation of collisions between cold atoms and cold ions. Cold collisions for laser cooled atoms in a MOT have been previously investigated for a number of systems, such as Cs + Cs and Rb + Rb, as well aas Rb + Cs, and others. The collisions between Cs atoms or Rb atoms in particular are of great interest in atomic clock development, where large collisional shifts in the clock frequency reduce the attainable uncertainties. Despite these studies, the collisional dynamics between laser cooled atoms and ions has not been as yet investigated. This is partially due to the challenge of combining trapped ions with cold atoms in a single apparatus.

At JPL, we are developing an apparatus which combines the linear trap used in our ion clocks with a 2-D MOT used in our quantum gravity gradiometer. This approach allows overlap of the ions with atoms with a volume large enough to yield high enough signal to noise ratio to allow a determination of the collisional cross sections. The apparatus will also allow observation of sympathetic cooling of ions with cold atoms, as well as the ability to transfer alignment and orientation from optically pumped atoms to ground state ions. Our base experiment will include mercury ions and rubidium atoms, to be followed with other species of interest.