We describe an experimental setup comprised of a discharge source for supersonic beams of metastable helium atoms and a magneto-optical trap (MOT) for ultracold lithium atoms that makes it possible to study Penning ionization and associative ionization processes at high ion count rates. The cationic reaction products are analyzed using a novel ion detection scheme which allows for mass selection, a high ion extraction efficiency and a good collision-energy resolution. The influence of elastic He-Li collisions on the steady-state Li atom number in the MOT is described, and the collision data are used to estimate the excitation efficiency of the discharge source. We also show that Penning collisions can be directly used to probe the temperature of the Li cloud without the need for an additional time-resolved absorption or fluorescence detection system.

We present a comparison of two technically distinct methods for the generation of rotationally cold, pulsed supersonic beams of methyl radicals (CH 3 ): a plate discharge source operating in the glow regime, and a dielectric barrier discharge source (DBD). The results imply that the efficiency of both sources is comparable, and that molecular beams with similar translational and rotational temperatures are formed. Methane (CH 4 ) proved to be the most suitable radical precursor species.

Discharge and electron-impact excitation lead to the production of metastable helium atoms in two metastable states, 2 1 S 0 and 2 3 S 1 . However, many applications require pure beams of one of these species or at least a detailed knowledge of the relative state populations. In this paper, we present the characterization of an original experimental scheme for the optical depletion of He(2 1 S 0 ) in a supersonic beam which is based on the optical excitation of the 4 1 P 1 ← 2 1 S 0 transition at 397 nm using a diode laser. From our experimental results and from a comparison with numerical calculations, we infer a near unit depletion efficiency at all beam velocities under study (1070 m/s ≤ v ≤ 1750 m/s). Since the technique provides a direct means to determine the singlet-to-triplet ratio in a pulsed supersonic helium beam, our results show that the intrabeam singlet-to-triplet ratio is different at the trailing edges of the gas pulse.

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A near-resonant rf field pumping the hyperfine transition between the two ground states of a -shaped dark resonance leads to a resonance tripling, each component displaying electromagnetically induced transparency (EIT). We investigate the three resonances under high spectral and temporal resolution. The triplet formation is analogous to that of the Mollow triplet but distinct in that the role played by the spontaneous emission rate is now taken by the one-photon scattering rate of the optical Raman transition. Complex phase relations exist between the three em fields under EIT conditions. We explain our observations using numerical solutions of the quantum master equation as well as a simple analytical dressed-state model.