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.

In optical two-dimensional Fourier-transform (2DFT) spectroscopy, understanding how the spectral line shape is affected by pulse propagation in the sample is crucial for an accurate interpretation of spectra. We report an experimental study of pulse propagation effects in 2DFT spectroscopy performed in a dense atomic vapor. The spectral line shape can be dramatically distorted due to high optical density as well as the physical thickness of a sample. The spectral distortion can be partially corrected by using a reference pulse copropagating with the signal combined with appropriate data processing.

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We report the hyperfine coupling constants for the 6d 2 D J states of 133 Cs using two-color absorption spectroscopy with sub-Doppler resolution. Two single-mode diode lasers resonantly excite cesium in a low-pressure vapor cell. The frequency scale is directly referenced to the ground hyperfine interval of 87 Rb using a radiofrequency modulation technique. The 6d 2 D 5/2 coupling constants are measured as A = −4.66± 0.04 MHz and B = 0.9± 0.8 MHz, agreeing with the literature. The 6d 2 D 3/2 coupling constants are measured as A = 16.34± 0.03 MHz and B = −0.1± 0.2 MHz, which significantly improve the precision of previous measurements.