A special bonding state between atoms has been created for the first time in a laboratory. Through the experiment, the atoms can now be polarized so that they are positively charged on one side and negatively charged on the other using a laser beam. The findings were published in the scientific journal Physical Review X.
Polarization of Atoms Using Laser Beam
The laser beam allowed the atoms to attract each other, resulting in a very special bonding state. However, it is much weaker than an ordinary molecule's bond between two atoms, but still measurable.
The polarized atoms cause the attraction, but the laser beam gives them the ability to do so, in the sense that it is a molecule of light and matter.
The effect has been predicted in theory for a long time. However, scientists at TU Wien's Vienna Center for Quantum Science and Technology (VCQ), in collaboration with the University of Innsbruck, have now measured this exotic atomic bond for the first time.
The interaction can be used to manipulate extremely cold atoms, and the effect may also play a role in the formation of molecules in space.
A positively charged atomic nucleus in an electrically neutral atom is surrounded by negatively charged electrons. It surrounded the atomic nucleus much like a cloud.
Prof. Philipp Haslinger explained that the charge distribution shifts slightly if an external electric field is applied. The positive charge is shifted slightly in one direction, and the negative charge is shifted slightly in the other direction. Then the atom suddenly has a positive and a negative side, which is now polarized.
Because light is simply an electromagnetic field that changes very quickly, the polarization effect can also be achieved with laser light. When several atoms are in close proximity, the laser light polarizes them all in the same direction, which means that positive is on the left and negative is on the right or vice versa. In both cases, two neighboring atoms turn opposite charges towards each other, resulting in an attractive force.
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An Experiment Conducted Using the Laser Beam
Mira Maiwöger from TU Wien, the first author of the publication, says that it is a very weak attractive force, so it is necessary to conduct the experiment very carefully to measure it.
"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," she said.
The atoms are first captured and cooled in a magnetic trap on an atom chip, a technique developed at the Atominstitut by Prof. Jörg Schmiedmayer's group. The trap is then turned off, releasing the atoms in free fall. At less than a millionth of a Kelvin, the atom cloud is ultracold, but it has enough energy to expand during the fall.
However, polarizing the atoms with a laser beam during this phase creates an attractive force between them, slowing the expansion of the atomic cloud-and this is how the attractive force is measured.
The experiment was successful for the first time in polarizing several atoms together in a controlled manner, resulting in a measurable, attractive force between them. The attractive force is a valuable tool for controlling cold atoms that could be useful in astrophysics.
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