Studies of ultracold Rydberg atoms and plasmas

Summary form only given. We report on recent experimental and theoretical investigations of highly excited atoms prepared from a dense atomic sample in a magneto-optical trap (MOT). The goals of the work are two-fold. First, by exciting atoms above the ionization potential (IP) we can study the properties of an ultracold plasma of electrons (T<1 K) and ions (T<1 mK). Second, tuning the excitation below the IP, we can populate high-lying Rydberg states whose atomic radii are comparable to the interparticle spacing, possibly spawning new collective phenomena. In our initial experiments we study Rydberg states. We collect 10/sup 7/ /sup 85/Rb atoms in the MOT at a density of 10/sup 10//cm/sup 3/. Atoms in the 5s ground state are excited into Rydberg states using single photon excitation.