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Deceleration, cooling, and trapping of atoms

H. Metcalf

Published Aug 12, 1984• 0 citations
OpenAlex

Abstract

A variety of calculations have been performed connected with laser cooling of atoms, many of them relevant to the experiments at NBS on this subject. Some of these have been tested and found to agree well with these experiments. We have designed, built, and tested various devices for use in these experiments. We have also done various calculations relevant to magnetic traps for cooled atoms. These are particularly well-suited for laser cooled atoms.

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Laser-cooling and trapping neutral atoms

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The NBS-Gaithersburg experiments on laser deceleration and cooling of atomic beams are reviewed. The laser-cooling process is presented as an example of « lumino-refrigeration » by optical pumping originally proposed by Kastler. Prospects for using laser-cooled atoms in magnetostatic or radiative atom traps are discussed.

Annales de Physique•Jan 1, 1985•2 citations

Laser cooling and electromagnetic trapping of neutral atoms

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Atoms in a thermal beam can be cooled, decelerated, and stopped using the radiation pressure from a nearly resonant laser beam. Several groups have already used this laser-cooling process on an atomic sodium beam. The techniques and results of the various experimental groups are reviewed, and applications of laser-cooled atoms, in particular the possibility of confining them in electromagnetic traps, are discussed.

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International Laser Science Conference•Jan 1, 1986•0 citations

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Significant advances have been made in the ability to control the motion of neutral atoms. Cooling and trapping atoms present new possibilities for studies of ultracold atoms and atomic interactions. The techniques of laser cooling and deceleration of atomic beams, magnetic and laser trapping of neutral atoms, and a number of recent advances in the use of radiative forces to manipulate atoms are reviewed.

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Applications of laser cooling and trapping to fundamental physics

Carl Wieman, Eric Cornell, M. Stephens

We are attempting to produce an atomic vapor that is so cold that the de Broglie wavelength is larger than the interparticle spacing. This is the condition needed to obtain Bose-Einstein condensation of a noninteracting gas. Our approach is to optically trap and cool atomic cesium and then load it into a purely magnetic trap for further cooling. In the course of this work we have investigated a number of magnetic traps and very low temperature collisions that are relevant to the success of this approach. In other work we are developing optical trapping techniques for the efficient collection of radioactive alkali isotopes. This work is aimed at measuring parity violation in these isotopes and thereby stringently testing the standard model of elementary particle physics. We have studied how to optimize the capture efficiency of atoms in an atomic vapor. We are currently developing cells that will allow the atoms to bounce off the walls until they are captured in the optical trap. The efficiency of this capture scheme will be discussed.

Annual Meeting Optical Society of America•Jan 1, 1992•0 citations

Decelerating Neutral Dipolar Molecules

Giel Berden, Hendrick L. Bethlem, Gerard Meijer

Slowing down atoms using laser cooling, together with techniques like magnetic trapping and evaporative cooling, has led to numerous exciting results over the last decade [1], with the realization of Bose-Einstein condensation as the most spectacular achievement [2]. Laser-cooling schemes are applicable to atoms since closed multilevel systems can be realized and many consecutive absorptionemission cycles can be induced. This leads to a significant momentum transfer from the photons of the laser to the atom, resulting in a change of the velocity of the atom. There currently is a great interest in producing cold molecules for the study of cold molecule-molecule collisions, molecular quantum collective effects, Doppler-free spectroscopy, frequency standards, as well as many other applications already realized for atoms [3]. Slowing down of neutral molecules, a prerequisite for being able to trap them, has proven to be considerably more difficult to be achieved, however. The above-mentioned laser-cooling scheme cannot be applied to slow down molecules as no simple closed-level systems can be found; the unavoidable off-resonant radiative decay of molecules from the excited state to other vibrational levels in the electronic ground state hampers efficient momentum transfer [4]. Once molecules are present at sufficiently low kinetic energies, below a fraction of a cm21, they can be trapped in various ways. Trapping of neutral molecules in inhomogeneous magnetic [3] and electric fields [5] and trapping based on the use of evanescent fields close to the dielectricvacuum interface have been proposed [6]. It has also been suggested that extremely high laser powers might be used to induce a dipole moment in polarizable molecules, leading to trapping of these molecules in the laser beam [7]. Other methods to produce slow molecules have been put forward and have recently been successfully applied to produce the first samples of trapped molecules. By injecting molecules in a cold buffer gas, sufficiently low kinetic energies of the injected molecules can be obtained after thermalization that they can subsequently be trapped in an inhomogeneous magnetic field. This has recently been demonstrated for CaH injected in 3He buffer gas at temperatures of around 0.3 K [8]. Associative collisions between ultracold trapped atoms [9] have proven to be

•Jan 1, 1999•134 citations
A variety of calculations have been performed connected with laser cooling of atoms, many of them relevant to the experiments at NBS on this subject. Some of these have been tested and found to agree well with these experiments. We have designed, built, and tested various devices for use in these experiments. We have also done various calculations relevant to magnetic traps for cooled atoms. These are particularly well-suited for laser cooled atoms.
Magnetic trapping of laser-cooled neutral atoms has been demonstrated at NBS and is progressing in other laboratories. Confinement of any object requires exchanging kinetic for potential energy, and for neutral atoms, this necessarily derives from shifts of internal energy levels. This is implemented through the force experienced by the atomic magnetic moment in a carefully designed, highly inhomogeneous field. Since magnetic fields of convenient strength can shift atomic energy levels by only a few gigahertz (temperature ≌ 0.1 K), neutral atom traps are very shallow and must be loaded with very cold atoms. We present some motivations for using magnetic traps and then discuss the constraints and optimal configurations of various arrangements. For example, no trap can be isotropic. Next we discuss both the classical and quantum mechanical motions of trapped atoms. These motions are important for at least two reasons: First, several schemes under study for further cooling depend on knowing the position and velocity of the atoms, as well as the vector field at each point along the orbit. Second, magnetic traps depend on the atomic moment remaining aligned with the field as the atom orbits in the trap, and this precludes rapid motion through a low-field region.
We are attempting to produce an atomic vapor that is so cold that the de Broglie wavelength is larger than the interparticle spacing. This is the condition needed to obtain Bose-Einstein condensation of a noninteracting gas. Our approach is to optically trap and cool atomic cesium and then load it into a purely magnetic trap for further cooling. In the course of this work we have investigated a number of magnetic traps and very low temperature collisions that are relevant to the success of this approach. In other work we are developing optical trapping techniques for the efficient collection of radioactive alkali isotopes. This work is aimed at measuring parity violation in these isotopes and thereby stringently testing the standard model of elementary particle physics. We have studied how to optimize the capture efficiency of atoms in an atomic vapor. We are currently developing cells that will allow the atoms to bounce off the walls until they are captured in the optical trap. The efficiency of this capture scheme will be discussed.
Slowing down atoms using laser cooling, together with techniques like magnetic trapping and evaporative cooling, has led to numerous exciting results over the last decade [1], with the realization of Bose-Einstein condensation as the most spectacular achievement [2]. Laser-cooling schemes are applicable to atoms since closed multilevel systems can be realized and many consecutive absorptionemission cycles can be induced. This leads to a significant momentum transfer from the photons of the laser to the atom, resulting in a change of the velocity of the atom. There currently is a great interest in producing cold molecules for the study of cold molecule-molecule collisions, molecular quantum collective effects, Doppler-free spectroscopy, frequency standards, as well as many other applications already realized for atoms [3]. Slowing down of neutral molecules, a prerequisite for being able to trap them, has proven to be considerably more difficult to be achieved, however. The above-mentioned laser-cooling scheme cannot be applied to slow down molecules as no simple closed-level systems can be found; the unavoidable off-resonant radiative decay of molecules from the excited state to other vibrational levels in the electronic ground state hampers efficient momentum transfer [4]. Once molecules are present at sufficiently low kinetic energies, below a fraction of a cm21, they can be trapped in various ways. Trapping of neutral molecules in inhomogeneous magnetic [3] and electric fields [5] and trapping based on the use of evanescent fields close to the dielectricvacuum interface have been proposed [6]. It has also been suggested that extremely high laser powers might be used to induce a dipole moment in polarizable molecules, leading to trapping of these molecules in the laser beam [7]. Other methods to produce slow molecules have been put forward and have recently been successfully applied to produce the first samples of trapped molecules. By injecting molecules in a cold buffer gas, sufficiently low kinetic energies of the injected molecules can be obtained after thermalization that they can subsequently be trapped in an inhomogeneous magnetic field. This has recently been demonstrated for CaH injected in 3He buffer gas at temperatures of around 0.3 K [8]. Associative collisions between ultracold trapped atoms [9] have proven to be