State selective charge transfer cross sections for Na+ with excited rubidium: a unique diagnostic of the population dynamics of a magneto-optical trap.

It is shown how the newly developed technique of magneto-optical-trap recoil-ion momentum spectroscopy can be used to measure the temporal evolution of excited state fraction in such a trap. In this case, the fraction of atoms in a 5p state is measured. The technique can be generalized to allow the measurement of more complicated systems, e.g., a Rb sample having a mixture of 5s, 5p, 4d, and Rydberg states.