Population dynamics in weakly excited clouds of ultracold ${}^{87}\text{R}\text{b}$ Rydberg atoms were studied by means of trap loss, fluorescence detection, and state-dependent stimulated emission. Rydberg atoms were excited to various $nl$ Rydberg states via continuous two-photon excitation from a magneto-optical trap. A stimulated emission probe laser was then used to bring the Rydberg atoms down to the $6P_{3/2}$ state, allowing state-dependent detection of the Rydberg atoms. Measurements of trap loss and fluorescent emission reveal information about the evolution of the Rydberg populations. In particular, population in the initial Rydberg state quickly transfers to other Rydberg states by a noncollisional mechanism, likely superradiant emission. The trap-loss measurements are consistent with black-body ionization as the dominant loss mechanism.

• Received 5 March 2008

DOI:https://doi.org/10.1103/PhysRevA.77.052712