https://link.aps.org/pdf/10.1103/RevModPhys.70.721

Nobel Lecture: Laser cooling and trapping of neutral atoms

We give a comprehensive overview of the development of micro traps, from the first experiments on guiding atoms using current carrying wires in the early 1990's to the creation of a BEC on an atom chip.

Microscopic atom optics: from wires to an atom chip

Publisher Summary This chapter focuses on the concept of evaporative cooling of trapped neutral atoms. The recent observations of Bose–Einstein condensation have shown dramatically the potential of evaporative cooling. Through evaporative cooling, phase-space density could be increased by six orders of magnitude in these experiments. In such experiments, evaporative cooling was used to reach temperature and densities that are unprecedented for trapped atoms and greatly exceeded what had been reached before by laser cooling. Laser cooling has recently broken the recoil limit in three dimensions (3D) and reached extremely cold temperatures of 3 nK in 1D. However, none of these optical sub-recoil techniques has been realized so far at high densities. The current density limitations are caused by the absorption of light, radiation trapping, and excited state collisions. An often-mentioned disadvantage of evaporative cooling is the loss of atoms. However, as discussed in the chapter, the efficiency of evaporative cooling is quite high.

Evaporative Cooling of Trapped Atoms

This paper reviews the basic theory of the mechanical action of light in resonant interaction with atoms. At present the main application is laser cooling, but the approach is applicable to a broader range of phenomena. It is based on an adiabatic elimination philosophy, which turns out to give the lowest-order quantum corrections to the behavior found when the photon momentum goes to zero. Hence it is called a semiclassical theory. In this manner a subjective but consistent approach can be presented; other treatments are incorporated or mentioned at the appropriate places. Both the classical and the quantum-mechanical approach are discussed. Those readers who wish to obtain only a heuristic overview of the phenomena can concentrate on Sec. III, which treats both the photon momentum effects and their connection with photon counting statistics. The detailed theoretical treatment utilizes Wigner functions and Fokker-Planck techniques. The ensuing theory is applied both to the cooling of free particles and trapped ones. The paper ends with an extensive bibliography, where the author lists most papers of interest for research into the mechanical manifestations of light. For completeness, many papers are included that are not explicitly mentioned in the text.

The semiclassical theory of laser cooling

The vibration-rotational spectrum of the hydrogen molecular ion H${\mathrm{D}}^{+}$ has been observed by means of a new ion-beam laser-resonance method employing Doppler-effect tuning and collisional detection Six transition-frequency groups between 1642 and 1869 ${\mathrm{cm}}^{\ensuremath{-}1}$, exhibiting partially resolved hyperfine structure, have been measured to \ifmmode\pm\else\textpm\fi{} 1 ppm The accuracy exceeds that of present theoretical calculations of H${\mathrm{D}}^{+}$ energy levels

Observation of the Infrared Spectrum of the Hydrogen Molecular Ion H D

A highly excited (Rydberg) atom bathed in blackbody radiation is perturbed in two ways. A dynamic Stark shift is induced by the off-resonant components of the blackbody radiation. Additionally, electric-dipole transitions to other atomic energy levels are induced by the resonant components of the blackbody radiation. This depopulation effect shortens the Rydberg-state lifetime, thereby broadening the energy level. Calculations of these two effects in many states of hydrogen, helium, and the alkali-metal atoms Li, Na, K, Rb, and Cs are presented for $T=300$ K. Contributions from the entire blackbody spectrum and from both discrete and continuous perturbing states are included. The accuracy is considerably greater than that of previous estimates.

Accurate calculation of dynamic Stark shifts and depopulation rates of Rydberg energy levels induced by blackbody radiation. Hydrogen, helium, and alkali-metal atoms

On neutral particle trapping in quasistatic electromagnetic fields

Electrostatic Trapping of Neutral Atomic Particles

The infrared vibrational-rotational spectrum of the ${\mathrm{D}}_{3}^{+}$ isotope of the simplest polyatomic molecule is observed. Eight intervals between 1750 and 1850 ${\mathrm{cm}}^{\ensuremath{-}1}$ have been measured to an error of 0.0005 ${\mathrm{cm}}^{\ensuremath{-}1}$ or 0.3 ppm (at 70% confidence level). Four have been identified as members of the fundamental degenerate vibrational band. The rest apparently involve unidentified higher vibrational-rotational levels.

William H. Wing

Papers

Observation of the Infrared Spectrum of the Hydrogen Molecular Ion H D

Accurate calculation of dynamic Stark shifts and depopulation rates of Rydberg energy levels induced by blackbody radiation. Hydrogen, helium, and alkali-metal atoms

On neutral particle trapping in quasistatic electromagnetic fields

Electrostatic Trapping of Neutral Atomic Particles

Observation of the Infrared Spectrum of the Triatomic Deuterium Molecular Ion D 3