Excitations in Systems of Trapped Cold Atoms

Lev Khaykovich, Nir Friedman, Roee Ozeri +2 more

Summary form only given. Utilizing cold and trapped atoms for precision spectroscopy of weak atomic transitions has two important advantages: the suppression of Doppler and time-of-flight broadenings and a combination of long interaction times, weak perturbations and tight confinement, which can be obtained using dark optical traps. We present a new and extremely sensitive method for measuring weak transitions with cold atoms in a dark optical trap, using electron shelving spectroscopy. Our scheme is based on a /spl Lambda/ system. Atoms with two ground states (for example, two hyperfine levels) are stored in the trap in a level that is coupled to the upper (excited) state, by an extremely weak transition. Atoms that undergo the weak transition may be shelved by a spontaneous Raman transition on the second ground level, which is uncoupled to the excited level by the measured photons. Finally, the detection scheme benefits from the multiply excited fluorescence of a strong closed transition from the uncoupled ground-state, that utilizes quantum amplification due to the electron shelving technique. We realized this scheme on a 5S/sub 1/2//spl rarr/5D/sub 5/2/ two-photon transition in cold and optically trapped /sup 85/Rb atoms.

Tomasz Brzozowski, Maria Brzozowska, Jerzy Zachorowski +1 more

Isabel Llorente‐Garcia, Benoît Darquié, Christopher D. J. Sinclair +4 more

We describe an experiment in which cold rubidium atoms, confined in an elongated magnetic trap, are excited by transverse oscillation of the trap center. The temperature after excitation exhibits resonance as a function of the driving frequency. We measure these resonances at several different trap frequencies. In order to interpret the experiments, we develop a simple model that incorporates both collisions between atoms and the anharmonicity of the real three-dimensional trapping potential. As well as providing a precise connection between the transverse harmonic oscillation frequency and the temperature resonance frequency, this model gives insight into the heating and loss mechanisms and into the dynamics of driven clouds of cold trapped atoms.

S. Stringari

Ya-Ping Ruan, Feng-Dong Jia, Long-Wei Liu +6 more

The temperature of the remaining cold 87 Rb atoms confined in a vapor cell magneto-optical trap after two-step photoionization has been measured. In the two-step photoionization process, the first excitation laser is served by the cooling laser and the second excitation laser is served by a continuous semiconductor laser with a wavelength of 450 nm. The results show that the temperature of the remaining cold atoms decreases as the intensity of the second excitation laser increases. Moreover, the relationship between the temperature T and number N of the remaining cold atoms generally follows a power law, while it deviates from the well-known T ∝ N 1/3 and the power factor is smaller than 1/3. We propose that ion-atom collisions occurring during a photoionization process strongly influence the temperature scaling law in an optically dense magneto-optical trap in the presence of an ionization laser. In addition, the forced evaporative cooling due to the combined effect of the detuning of the first excitation laser and the two-step photoionization plays a role in cooling the remaining cold atoms and results in the dependence of the power factor on the detuning of the first excitation laser.