Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Hints of universal behavior seen in exotic 3-atom states

26.09.2011
A novel type of inter-particle binding predicted in 1970 and observed for the first time in 2006, is forming the basis for an intriguing kind of ultracold quantum chemistry.

Chilled to nano-kelvin temperatures, cesium atoms---three at a time---come together to form a bound state hundreds or even thousands of times larger than individual atoms. Unlike the case of ordinary atoms, wherein electrons are bound to a nucleus in a spectrum of energy levels on the order of an electron volt (that is, it would typically take an eV of energy to free the electron), the cesium triplets feature energy levels that are measured in trillionths of an electron volt (peV). Stranger still, a new experiment observing four such cesium states reports that the states' sizes are roughly the same. This has taken theorists by complete surprise.

In the seventeenth century Isaac Newton derived the classical force laws used to calculate the force between two objects. Calculating the behavior of three-body groupings such as the Moon/Earth/Sun system was much harder; indeed Newton never succeeded. Nowadays such problems can be studied with powerful computers, but only numerical simulations are possible, and not exact, analytical solutions.

In 1970, however, Russian physicist Vitaly Efimov predicted that under some special conditions, three bodies, such as atoms at ultralow temperatures, could be made to enter into stable states whose behavior could be calculated with remarkable ease. Then in 2006 exactly such states were actually observed by scientists at the University of Innsbruck. Now, these researchers have extended their work and demonstrated that the "three-body parameter," used to describe how the three participating bodies interact, varies in a consistent way regardless of the atomic species used.

Paul Julienne, a scientist at the Joint Quantum Institute (JQI), operated by the University of Maryland and the National Institute of Standards and Technology (NIST), contributed theoretical help to the Innsbruck scientists conducting the experiment, a team led by Rudolf Grimm. "None of the experts in three-body physics had expected this kind of universal behavior to show up in these 3-atom systems," Julienne said. "This behavior came as a big surprise." And the universality, in turn, might suggest the existence of some new kind of ultracold chemistry at work.

Efimov's 1970 work met with much skepticism, especially since his prediction specified that three particles could form stable partnerships even though none of the two-particle matchups were stable. That is, 3 particles could accomplish what 2 particles could not. This novel arrangement has been compared to the "Borromean Rings," a set of three rings used on heraldic symbol for the Borromeo family during the Italian Renaissance. The three rings hold together unless any one of the rings is removed.

Efimov's prediction applies not just to atoms but to any 3 particles. For example, helium-6, a semi-stable nucleus consisting of 2 protons and 4 neutrons, can be made by from a helium-4 nucleus and 2 extra neutrons. The 2 neutrons cannot form a stable composite; neither can He-4 plus 1 extra neutron. But the three-body He4-n-n system is stable, at least for a while.

Such Borromean nuclei have been known for some time, but atoms have turned out to be more useful in pursuing the novel interactions called for in Efimov's theory. That's because atoms can be chilled to nano-kelvin temperatures in traps and made to interact with great precision. As atoms cool down, they get larger---at least in a quantum sense: as waves, their equivalent wavelength can be many times larger than their nominal particle size (a hydrogen atom is about 0.1 nm across). Furthermore, by applying an external magnetic field, subtle interactions among neutral atoms can be achieved.

Such interactions, called Feshbach resonances, were used to bring cesium atoms together, three at a time, in Efimov states. These atoms were part of a vapor held at temperatures of tens of nano-K. In 2006 the Innsbruck team reported seeing one such troika of atoms. Now, in the 16 September 2011 issue of Physical Review Letters, the Innsbruck-JQI-Durham researchers are reporting the observation of three more state of 3 atoms bound together.

These trimers are quantum objects; they have no classical counterpart. The weak binding of the super-cold Cs atoms is described in terms of a parameter, a, called the scattering length. If a is positive and large (much larger than the nominal range of the force between the atoms), weak binding of atoms can happen. If a is negative, a slight attraction of two atoms can occur but not binding. If, however, a is large, negative, and three atoms are present, then the Efimov state can appear. Indeed an infinite number of such states can occur. The Efimov state has an energy spectrum, as if it were a chemical element all by itself, with each binding energy level scaling with the value of a. This kind of universal behavior was expected.

The effective size of these Efimov-triplets is referred to as the three-body parameter. In the case of the four cesium states seen so far, the value is just about the same, about 50 nm, or about 500 times the size of a hydrogen atom. This, combined with the three-body-parameter values observed in experiments for lithium and possibly for other elements being studied right now, suggests that while adjusting for the size of the respective atoms all the species are behaving in the same way. This kind of universality was totally unexpected.

"It is really amazing how the new research field developed since we found the first traces of Efimov states, "said Grimm. "Now things have become reality, things we did not even dream about five years ago."

"Universality of the Three-Body Parameter for Efimov States in Ultracold Cesium," by M. Berninger, A. Zenesini,1 B. Huang, W. Harm, H.-C. Na¨gerl, F. Ferlaino, R. Grimm, P. S. Julienne, and J. M. Hutson, 16 September 2001 Physical Review Letters.

The Joint Quantum Institute (JQI), located in College Park, Maryland, is operated by the University of Maryland and the National Institute of Standards and Technology (NIST).

Phillip F. Schewe | EurekAlert!
Further information:
http://jqi.umd.edu/

More articles from Physics and Astronomy:

nachricht Tune your radio: galaxies sing while forming stars
21.02.2017 | Max-Planck-Institut für Radioastronomie

nachricht Breakthrough with a chain of gold atoms
17.02.2017 | Universität Konstanz

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: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Impacts of mass coral die-off on Indian Ocean reefs revealed

21.02.2017 | Earth Sciences

Novel breast tomosynthesis technique reduces screening recall rate

21.02.2017 | Medical Engineering

Use your Voice – and Smart Homes will “LISTEN”

21.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>