Positronium Laser Cooling via the 1

We report on laser cooling of a large fraction of positronium (Ps) in free flight by strongly saturating the 1^{3}S-2^{3}P transition with a broadband, long-pulsed 243 nm alexandrite laser. The ground state Ps cloud is produced in a magnetic and electric field-free environment. We observe two different laser-induced effects. The first effect is an increase in the number of atoms in the ground state after the time Ps has spent in the long-lived 2^{3}P states. The second effect is one-dimensional Doppler cooling of Ps, reducing the cloud's temperature from 380(20) to 170(20) K. We demonstrate a 58(9)% increase in the fraction of Ps atoms with v_{1D}<3.7×10^{4} ms^{-1}.

Low divergence cold-wall oven for loading ion traps.

We present a compact cold-wall oven that is simple to build and align for loading miniature ion traps with calcium ions. The cold-wall oven, which is a metal-loaded capillary heated only through a portion of its length by the passage of a current, is described and characterized. An atomic beam with a low divergence of 14 mrad is produced. We perform Doppler-sensitive, resonant fluorescence measurements on the atomic beam to characterize the oven's performance. The emission of atoms from the oven is seen within ∼70 s after turning on the oven at an electric power consumption of <10 W. The flow rate is measured to be 1.5 ± 0.2 × 109 atoms s-1 at a temperature of 702 ± 7 K. The entire oven assembly is mounted on a CF16 feedthrough. This design can be extended to other species for producing a collimated atomic beam.

Lasing by driven atoms-cavity system in collective strong coupling regime.

The interaction of laser cooled atoms with resonant light is determined by the natural linewidth of the excited state. An optical cavity is another optically resonant system where the loss from the cavity determines the resonant optical response of the system. The near resonant combination of an optical Fabry-Pérot cavity with laser cooled and trapped atoms couples two distinct optical resonators via light and has great potential for precision measurements and the creation of versatile quantum optics systems. Here we show how driven magneto-optically trapped atoms in collective strong coupling regime with the cavity leads to lasing at a frequency red detuned from the atomic transition. Lasing is demonstrated experimentally by the observation of a lasing threshold accompanied by polarization and spatial mode purity, and line-narrowing in the outcoupled light. Spontaneous emission into the cavity mode by the driven atoms stimulates lasing action, which is capable of operating as a continuous wave laser in steady state, without a seed laser. The system is modeled theoretically, and qualitative agreement with experimentally observed lasing is seen. Our result opens up a range of new measurement possibilities with this system.

Collisional Cooling of Light Ions by Cotrapped Heavy Atoms.

We experimentally demonstrate cooling of trapped ions by collisions with cotrapped, higher-mass neutral atoms. It is shown that the lighter ^{39}K^{+} ions, created by ionizing ^{39}K atoms in a magneto-optical trap (MOT), when trapped in an ion trap and subsequently allowed to cool by collisions with ultracold, heavier ^{85}Rb atoms in a MOT, exhibit a longer trap lifetime than without the localized ^{85}Rb MOT atoms. A similar cooling of trapped ^{85}Rb^{+} ions by ultracold ^{133}Cs atoms in a MOT is also demonstrated in a different experimental configuration to validate this mechanism of ion cooling by localized and centered ultracold neutral atoms. Our results suggest that the cooling of ions by localized cold atoms holds for any mass ratio, thereby enabling studies on a wider class of atom-ion systems irrespective of their masses.

Photodissociation of Trapped Rb_{2}

The direct photodissociation of trapped ^{85}Rb_{2}^{+} (rubidium) molecular ions by the cooling light for the ^{85}Rb magneto-optical trap (MOT) is studied, both experimentally and theoretically. Vibrationally excited Rb_{2}^{+} ions are created by photoionization of Rb_{2} molecules formed photoassociatively in the Rb MOT and are trapped in a modified spherical Paul trap. The decay rate of the trapped Rb_{2}^{+} ion signal in the presence of the MOT cooling light is measured and agreement with our calculated rates for molecular ion photodissociation is observed. The photodissociation mechanism due to the MOT light is expected to be active and therefore universal for all homonuclear diatomic alkali metal molecular ions.

Cooling and stabilization by collisions in a mixed ion-atom system.

In mixed systems of trapped ions and cold atoms, the ions and atoms can coexist at different temperatures. This is primarily due to their different trapping and cooling mechanisms. The key questions of how ions can cool collisionally with cold atoms and whether the combined system allows stable coexistence, need to be answered. Here we experimentally demonstrate that rubidium ions cool in contact with magneto-optically trapped rubidium atoms, contrary to the general experimental expectation of ion heating. The cooling process is explained theoretically and substantiated with numerical simulations, which include resonant charge exchange collisions. The mechanism of single collision swap cooling of ions with atoms is discussed. Finally, it is experimentally and numerically demonstrated that the combined ion-atom system is intrinsically stable, which is critical for future cold chemistry experiments with such systems.

Investigation of antirelaxation coatings for alkali-metal vapor cells using surface science techniques.

Many technologies based on cells containing alkali-metal atomic vapor benefit from the use of antirelaxation surface coatings in order to preserve atomic spin polarization. In particular, paraffin has been used for this purpose for several decades and has been demonstrated to allow an atom to experience up to 10 000 collisions with the walls of its container without depolarizing, but the details of its operation remain poorly understood. We apply modern surface and bulk techniques to the study of paraffin coatings in order to characterize the properties that enable the effective preservation of alkali spin polarization. These methods include Fourier transform infrared spectroscopy, differential scanning calorimetry, atomic force microscopy, near-edge x-ray absorption fine structure spectroscopy, and x-ray photoelectron spectroscopy. We also compare the light-induced atomic desorption yields of several different paraffin materials. Experimental results include the determination that crystallinity of the coating material is unnecessary, and the detection of C[Double Bond]C double bonds present within a particular class of effective paraffin coatings. Further study should lead to the development of more robust paraffin antirelaxation coatings, as well as the design and synthesis of new classes of coating materials.

Trapping of neutral rubidium with a macroscopic three-phase electric trap.

We trap neutral ground-state rubidium atoms in a macroscopic trap based on purely electric fields. For this, three electrostatic field configurations are alternated in a periodic manner. The rubidium is precooled in a magneto-optical trap, transferred into a magnetic trap, and then translated into the electric trap. The electric trap consists of six rod-shaped electrodes in cubic arrangement, giving ample optical access. Up to 10;{5} atoms have been trapped with an initial temperature of around 20 microkelvin in the three-phase electric trap. The observations are in good agreement with detailed numerical simulations.

Continuous loading of an electrostatic trap for polar molecules.

A continuously operated electrostatic trap for polar molecules is demonstrated. The trap has a volume of approximately 0.6 cm3 and holds molecules with a positive Stark shift. With deuterated ammonia from a quadrupole velocity filter, a trap density of approximately 10(8) cm(-3) is achieved with an average lifetime of 130 ms and a motional temperature of approximately 300 mK. The trap offers good starting conditions for high-precision measurements, and can be used as a first stage in cooling schemes for molecules and as a "reaction vessel" in cold chemistry.

Two-dimensional trapping of dipolar molecules in time-varying electric fields.

Simultaneous two-dimensional trapping of neutral dipolar molecules in low- and high-field seeking states is analyzed. A trapping potential of the order of 20 mK can be produced for molecules such as ND3 with time-dependent electric fields. The analysis is in agreement with an experiment where slow molecules with longitudinal velocities of the order of 20 m/s are guided between four 50 cm long rods driven by an alternating electric potential at a frequency of a few kHz.

Atom laser divergence.

We measure the angular divergence of a quasicontinuous, rf-outcoupled, free-falling atom laser as a function of the outcoupling frequency. The data are compared to a Gaussian-beam model of laser propagation that generalizes the standard formalism of photonic lasers. Our treatment includes diffraction, magnetic lensing, and interaction between the atom laser and the condensate. We find that the dominant source of divergence is the condensate-laser interaction.