An Antimatter Experiment Reveals Surprises Close to Absolute Zero


The undertaking was designed to see if spectroscopy in a helium bathtub was doable in any respect—a proof of idea for future experiments that might use much more unique hybrid atoms.

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However Sótér was inquisitive about how the hybrid atoms would react to totally different temperatures of helium. She satisfied the collaboration to spend valuable antimatter repeating the measurements inside more and more chilly helium baths.

“It was a random concept from my aspect,” mentioned Sótér, now a professor on the Swiss Federal Institute of Expertise Zurich. “Individuals weren’t satisfied it was value it to waste antiprotons on it.”

The place the spectral traces of most atoms would have gone fully haywire within the more and more dense fluid, widening maybe 1,000,000 instances, the Frankenstein atoms did the other. Because the researchers lowered the helium bathtub to icier temperatures, the spectral smudge narrowed. And beneath about 2.2 kelvins, the place helium turns into a frictionless “superfluid,” they noticed a line almost as sharp because the tightest they’d seen in helium gasoline. Regardless of presumably taking a battering from the dense environment, the hybrid matter-antimatter atoms had been appearing in inconceivable unison.

Not sure what to make of the experiment, Sótér and Hori sat on the end result whereas they mulled over what might have gone flawed.

“We continued to argue for a few years,” Hori mentioned. “It was not really easy for me to grasp why this was the case.”

A Shut Name

In time, the researchers concluded that nothing had gone awry. The tight spectral line confirmed that the hybrid atoms in superfluid helium aren’t experiencing atomic collisions within the billiard-ball method that’s typical in a gasoline. The query was why. After consulting with varied theorists, the researchers landed on two doable causes.

One includes the character of the liquid environment. The atomic spectrum abruptly tightened when the group chilled the helium right into a superfluid state, a quantum mechanical phenomenon the place particular person atoms lose their identification in a manner that lets them circulation collectively with out rubbing in opposition to each other. Superfluidity takes the sting off atomic collisions on the whole, so researchers count on international atoms to expertise solely delicate broadening or perhaps a restricted quantity of tightening in some instances. “Superfluid helium,” Lemeshko mentioned, “is the softest identified factor you may immerse atoms and molecules into.”

However whereas superfluid helium could have helped the hybrid atoms develop into their most isolationist selves, that alone can’t clarify simply how nicely behaved the atoms had been. One other key to their conformity, the researchers consider, was their uncommon construction, one led to by their antimatter part.

In a standard atom, a tiny electron can enterprise removed from its host atom, particularly when excited by a laser. On such a unfastened leash, the electron can simply stumble upon different atoms, disturbing its atom’s intrinsic vitality ranges (and resulting in spectral broadening).

When Sótér and her colleagues swapped zippy electrons for lumbering antiprotons, they drastically modified the atom’s dynamics. The huge antiproton is rather more of a homebody, staying near the nucleus the place the outer electron can shelter it. “The electron is sort of a drive area,” Hori mentioned, “like a protect.”


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