Tessa Koumounduros
WALL – “For the first time, we have succeeded in creating a measurable attractive force between them by polarizing a few atoms in a controlled way,” says Matthias Sonnleitner, a physicist at the University of Innsbruck.
Atoms bond together in different ways to form molecules, and all engage in an exchange of charges, acting as a kind of ‘superglue’.
Some of these form relatively strong bonds with complex hydrocarbons floating in space by sharing their negatively charged electrons, just like the simplest gases formed by two bonded oxygen atoms that we breathe incessantly. Some atoms are due to differences in their total charges. [diğerlerini] they pull.
Electromagnetic fields can change the order of charges around an atom. Since light is a rapidly changing electromagnetic field, a suitably directed shower of photons can – theoretically – push electrons into positions where we can see their bonds.
“If you activate an external electric field, this charge distribution changes slightly,” explains Philipp Haslinger, a physicist at the Technical University of Vienna (TU Wien).
“The positive charge shifts slightly in one direction, the negative charge slightly shifts in the other; so the atom is suddenly polarized, having positive and negative sides [kutuplaştırılır].”
Mira Maiwöger, an atomic physicist at Haslinger, TU Wien, and colleagues used extremely cold rubidium atoms to show that light can polarize atoms in the same way, causing neutral atoms to become partially ‘sticky’.
Maiwöger said, “This is a very weak attractive force; so you have to perform the experiment very carefully to be able to measure.”
“If atoms contain an excess of energy and are moving rapidly, the attractive force disappears immediately. For this reason, we used an extremely cold atom cloud.”
The research team used a magnetic field to trap a cloud of about 5,000 atoms in a single plane under a gold-plated chip.
This is a quasicondensate, cooling atoms to temperatures approaching absolute zero (-273°C). [yarı-yoğuşuk madde] where they are created; in this way, rubidium particles begin to act en masse and share properties as if they were in the fifth state of matter, though not to the exact same extent.
Atoms hit with a laser are subjected to various forces. For example, the radiation pressure carried by incoming photons can push them along a beam of light. Meanwhile, the reactions occurring in the electrons can pull the atom back towards the most intense part of the beam.
Researchers had to do some precise calculations to detect the weak gravitational force thought to arise between atoms in this stream of electromagnetism.
When they turn off the magnetic field, [oluşan] The atoms were subjected to free fall for about 44 milliseconds before the light layer reached the laser light field, where they were also imaged using a fluorescent microscope.
During the fall, the cloud naturally expanded; In this way, the researchers were able to perform measurements at different intensities.
Maiwöger and colleagues noticed that at high densities, 18 percent of the atoms were missing from the observation images they recorded. They think these gaps are caused by light-assisted collisions that blast rubidium atoms out of clouds.
This finding revealed some of what was going on; that is, it was not only the incident light that affected the atoms, but also the light scattered from other atoms. When light touched atoms, it polarized them.
Atoms were attracted or repelled by greater light intensity, depending on the type of light used. In this way, they were either drawn towards the lower light or higher light region and in any case began to accumulate en masse.
In their paper, Maiwöger and colleagues wrote, “With known radiation forces, [ışıkla tetiklenen] “The main difference between the interaction is that the latter is an effective interparticle interaction mediated by scattered light.”
“It doesn’t hold atoms in a fixed position (like the focus of a laser beam); however, it pulls them towards regions with the highest particle density.”
BIG EFFECT OF SMALL FORCES
This force that brings atoms together, though much weaker than the more familiar molecular forces, can add up on large scales. This can change emission patterns and resonance lines, features that astronomers use to help us understand celestial bodies.
It could also help explain how molecules in space form. “In the vastness of space, small forces can play a remarkable role,” Haslinger says.
“Here we have demonstrated for the first time that electromagnetic radiation can create a force between atoms; this could help shed new light on astrophysical scenarios that have yet to be explained.”
The research was published in the scientific journal Physical Review X.
Source: Science Alert
Translated by: Tarkan Tufan
–
