Radiative lifetime measurements of rubidium Rydberg states

Abstract

We have measured the radiative lifetimes of ns, np and nd Rydberg states of\nrubidium in the range 28 < n < 45. To enable long-lived states to be measured,\nour experiment uses slow-moving Rb atoms in a magneto-optical trap (MOT). Two\nexperimental techniques have been adopted to reduce random and systematic\nerrors. First, a narrow-bandwidth pulsed laser is used to excite the target\nRydberg state, resulting in minimal shot-to-shot variation in the initial state\npopulation. Second, we monitor the target state population as a function of\ntime delay from the laser pulse using a short-duration, millimetre-wave pulse\nthat is resonant with a one- or two-photon transition. We then selectively\nfield ionize the monitor state, and detect the resulting electrons with a\nmicro-channel plate. This signal is an accurate mirror of the target state\npopulation, and is uncontaminated by contributions from other states which are\npopulated by black body radiation. Our results are generally consistent with\nother recent experimental results obtained using a less sensitive method, and\nare also in excellent agreement with theory.\n