Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

First observation of an ’Atomic Air Force’

20.08.2004


The first sighting of atoms flying in formation has been reported by physicists at the Department of Commerce’s National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder (CU-Boulder) in the Aug. 13 issue of Physical Review Letters*. While the Air Force and geese prefer a classic "V," the strontium atoms--choreographed in this experiment with precision laser pulses and ultracold temperatures--were recorded flying in the shape of a cube.


These colorized images show strontium atoms forming a "cube" as the frequency of laser light used to manipulate them changes. (Left) Atoms become visible at the eight corners of a cube. (Middle) Atoms also appear at the midpoints of the lines forming each cube face and begin to appear at the center of each cube face. Right) Atoms appear at the corners, as well as at the midpoints and more clearly at the centers of each cube face.



This "really bizarre" behavior is believed to occur with all atoms under similar conditions, says physicist Jun Ye of NIST, who led the research at JILA, a joint institute of NIST and CU-Boulder. Ye is also a faculty member of the CU-Boulder physics department."

Atoms have not previously been seen flying in formation, says Ye. Strontium’s unique physical properties make the observations possible. In particular, the configuration of strontium’s electrons and the resulting atomic properties allow it to efficiently absorb laser energy in two very specific "resonant" wavelengths--a strong resonance at a wavelength of blue light and another, much weaker resonance for longer-wavelength red light. This makes strontium a promising candidate for a next-generation atomic clock based on optical rather than microwave frequencies, and is the reason the JILA team is studying the atom’s quantum behavior (see text box at right).


The experiment was conducted with a dense gaseous cloud of 100 million strontium atoms. The atoms were held in the center of a vacuum chamber with both a magnetic field and six intersecting laser beams, in three sets of facing pairs aligned at right angles to each other. The atoms, which were very hot initially at 800 Kelvin (980 degrees F), were trapped with the magnetic field and blue laser light and cooled to 1 milliKelvin. Then with red laser light, the atoms were rapidly cooled further to about 250 nanoKelvin (almost absolute zero, or minus 459 degrees F).

At this point, the magnetic field was turned off, and the red laser beams were tuned to a slightly higher frequency than strontium’s weak, red resonance frequency. This caused the atoms to fly apart in cubic formation. The shape was observed in a series of images (see graphic) by hitting the atoms with blue laser light. The atoms absorb the laser energy by shifting an outermost electron to a higher energy orbit but then very quickly decay back to the lower energy state by re-emitting blue light. Even though different atomic packets are flying away at different speeds and directions, the strong blue fluorescence signals emitted from the atoms can be recorded with a camera, and all of the atoms can be visualized at the same time.

The flying structure was created in part by a recoil effect--the momentum kick received by the atoms as they absorbed or emitted each particle of light, or photon. This effect is similar to the recoil received when shooting a gun, Ye says. When an atom absorbs photons from a laser beam, it is pushed in the same direction as the incoming beam. The Doppler effect--the same reason that a train’s whistle sounds lower as it moves away from you--causes the incoming laser beam, as the atoms fly away, to appear to have a slightly lower frequency, moving closer to the atom’s resonant frequency. Meanwhile, the opposing laser beam appears to have a higher frequency as the atoms rush toward it, and falls farther out of resonance. Strontium atoms very quickly stop responding to the latter beam and fly off in the same direction as the resonant beam.

The combined effect of all six incident beams makes the atoms fly away in cube-shaped clusters. The research team captured images of the atoms flying in clusters at speeds of about 10 to 15 centimeters per second. The cubic arrangement of the atomic clusters changes as the intensity and frequency of the red light varies. The corners of the cube appear first, when the laser light is tuned relatively close to the atomic resonance. As the red light is tuned further above the atomic resonance frequency, atomic clusters appear at the mid-points of all sides of the cube, as well as eventually at the centers of each face.

Ye conducted the work and co-authored the paper with JILA postdoctoral research associates Thomas H. Loftus and Tetsuya Ido, and CU-Boulder doctoral candidates Andrew D. Ludlow and Martin M. Boyd.

Funding for the project was provided by the Office of Naval Research, the National Science Foundation, the National Aeronautics and Space Administration, and NIST.

As a non-regulatory agency of the U.S. Department of Commerce’s Technology Administration, NIST develops and promotes measurement, standards and technology to enhance productivity, facilitate trade and improve the quality of life.

* Thomas H. Loftus, Tetsuya Ido, Andrew D. Ludlow, Martin M. Boyd, and Jun Ye. 2004. Narrow Line Cooling: Finite Photon Recoil Dynamics. Physical Review Letters 93(7), Aug. 13.

Laura Ost | EurekAlert!
Further information:
http://www.nist.gov

More articles from Physics and Astronomy:

nachricht Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst

nachricht Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>