Abstract. We have measured the radiative lifetimes of ns, np and nd Rydberg states of rubidium in the range 28 ≤ n ≤ 45. To enable long-lived states to be measured, our experiment uses slow-moving (∼100 µK) 85 Rb atoms in a magnetooptical trap (MOT). Two experimental techniques have been adopted to reduce random and systematic errors. First, a narrow-bandwidth pulsed laser is used to excite the target nℓ Rydberg state, resulting in minimal shot-to-shot variation in the initial state population. Second, we monitor the target state population as a function of time delay from the laser pulse using a short-duration, millimetre-wave pulse that is resonant with a one-or two-photon transition to a higher energy "monitor state", n ′ ℓ ′ . We then selectively field ionize the monitor state, and detect the resulting electrons with a micro-channel plate. This signal is an accurate mirror of the nℓ target state population, and is uncontaminated by contributions from other states which are populated by black body radiation. Our results are generally consistent with other recent experimental results obtained using a method which is more prone to systematic error, and are also in excellent agreement with theory.

This thesis discusses progress towards achieving external control of the electron temperature and the Coulomb coupling parameter of ultra-cold plasmas.Using a Littman dye laser, we create the plasma by partially photoionizing a dense, cold sample of rubidium atoms in a magneto-optical trap (MOT). At a controllable time delay, we excite neutral atoms in the plasma to a specific Rydberg state using a narrow bandwidth pulsed dye laser. We have made progress towards optimizing and quantifying the achievable Rydberg atom density by using mm-wave spectroscopy to control the evolution of a cold dense Rydberg sample to plasma and have also begun preliminary investigations of plasma electron temperature measurements.i