Theoretically, this effect has been predicted for a long time, but now scientists at the Vienna Center for Quantum Science and Technology (VCQ) at TU Wien, in cooperation with the University of Innsbruck, have succeeded in measuring this exotic atomic bond for the first time. This interaction is useful for manipulating extremely cold atoms, and the effect could also play a role in the formation of molecules in space. The results have now been published in the scientific journal Physical Review X.
Positive and negative charge
In an electrically neutral atom, a positively charged atomic nucleus is surrounded by negatively charged electrons, which surround the atomic nucleus much like a cloud. "If you now switch on an external electric field, this charge distribution shifts a little," explains Prof. Philipp Haslinger, whose research at the Atominstitut at TU Wien is supported by the FWF START programme. "The positive charge is shifted slightly in one direction, the negative charge slightly in the other direction, the atom suddenly has a positive and a negative side, it is polarised."
Light is just an electromagnetic field that changes very rapidly, so it is also possible to create this polarisation effect with laser light. When several atoms are next to each other, the laser light polarises them all in exactly the same way - positive on the left and negative on the right, or vice versa. In both cases, two neighbouring atoms turn different charges towards each other, leading to an attractive force.
Experiments with the atom trap
"This is a very weak attractive force, so you have to conduct the experiment very carefully to be able to measure it," says Mira Maiwoger from TU Wien, the first author of the publication. "If atoms have a lot of energy and are moving quickly, the attractive force is gone immediately. This is why a cloud of ultracold atoms was used."
The atoms are first captured and cooled in a magnetic trap on an atom chip, a technique, which was developed at the Atominstitut in the group of Prof. Jorg Schmiedmayer. Then the trap is switched off and releases the atoms in free fall. The atom cloud is 'ultracold' at less than a millionth of a Kelvin, but it has enough energy to expand during the fall. However, if the atoms are polarized with a laser beam during this phase and thus an attractive force is created between them, this expansion of the atomic cloud is slowed down - and this is how the attractive force measured.
Quantum laboratory and space
"Polarising individual atoms with laser beams is basically nothing new," says Matthias Sonnleitner, who laid the theoretical foundation for the experiment. "The crucial thing about our experiment, however, is that we have succeeded for the first time in polarising several atoms together in a controlled way, creating a measurable attractive force between them."
This attractive force is a complementary tool for controlling cold atoms. But it could also be important in astrophysics: "In the vastness of space, small forces can play a significant role," says Philipp Haslinger. "Here, we were able to show for the first time that electromagnetic radiation can generate a force between atoms, which may help to shed new light on astrophysical scenarios that have not yet been explained."
|Thanks for being there;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.
With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.
Our news coverage takes time and effort to publish 365 days a year.
If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
|SpaceDaily Monthly Supporter
$5+ Billed Monthly
$5 Billed Once credit card or paypal
When particles move
Santa Barbara CA (SPX) Aug 03, 2022
Landslides are one striking example of erosion. When the bonds that hold particles of dirt and rock together are overwhelmed by a force - often in the form of water - sufficient to pull the rock and soil apart, that same force breaks the bonds with other rock and soil that hold them in place. Another type of erosion involves using a small air jet to remove dust from a surface. When the force of the turbulent air is strong enough to break the bonds that hold the individual dust particles, or grains ... read more