The quantum physical phenomenon is typical of helium at extremely low temperatures. "The lines that were very broad at higher temperatures became narrow." The superfluid phase is a special liquid state that is characterised, among other things, by the absence of internal friction. The surprising discovery: "If the temperature dropped below the critical temperature of 2.2 Kelvin – 2.2 degrees Celsius above absolute zero - at which helium enters a superfluid state, the shape of the spectral lines suddenly changed," reports Anna Sótér, who was the principal PhD student of the team at the Max Planck Institute for Quantum Optics in this project and recently promoted as assistant professor of ETH Zürich. To do this, they irradiated the liquid helium with light from a titanium-sapphire laser, which excited two characteristic resonances of the antiprotonic atoms at two different frequencies.
Laser wolf liquid series#
In a series of experiments, the scientists took a spectroscopic look at the antiprotonic helium atoms at different temperatures. Hori and his team have now succeeded for the first time in preventing the "smearing" of the spectral lines in a liquid. But the broadening of the lines obscures this information because it is virtually smeared. The exact position of the resonance line on the frequency scale as well as the shape reveal the properties of the atom under investigation - and the forces acting on the antiparticle. They are thus a kind of fingerprint that identifies each atom. These lines are images of resonances in which the energy absorbed from the laser beam excites the atoms. This is because the intense interactions between the densely packed atoms or molecules of the liquid lead to a strong broadening of the spectral lines. "Until now, it was thought that antimatter atoms embedded in liquids could not be investigated by high resolution spectroscopy using laser beams," Hori reports. The antiproton replaced one of the two electrons that normally surround a helium atomic nucleus - forming a structure that remained stable long enough to be studied spectroscopically. The researchers mixed the slow antiprotons with liquid helium cooled to a temperature of a few degrees above absolute zero, or minus 273 degrees Celsius, trapping a small part of the antiprotons in atoms of helium. The slow velocity of the antiprotons makes them ideal for experiments such as those conducted by Hori's team. To create the exotic helium atoms containing antiprotons, the researchers used the Antiproton Decelerator at Cern - a globally unique facility that slows down the antimatter particles created in collisions of energetic protons. With his team's latest findings, however, the Garching physicist has paved the way for a different application of antimatter by optical spectroscopy of antiprotonic helium atoms in a superfluid environment. “Our team has previously used this hybrid helium atom to precisely compare the masses of antiprotons and electrons.” Other experiments have confined antiprotons in ion traps made of electric and magnetic fields," Hori explains. "To do this, atoms of antimatter have been magnetically levitated in vacuum chambers for spectroscopic measurements. That's why scientists around the world are fine-tuning various techniques to scrutinise the characteristics of antiparticles with ever greater precision. The results of the experiments carried out at the European Organization for Nuclear Research CERN in Geneva surprised the scientists because of the precise and sensitive way that the antimatter-matter hybrid atoms reacted to laser light despite the dense liquid that surrounded the atoms.īut perhaps the available experimental methods are just not sensitive enough to detect any subtle differences that might exist? "We can‘t rule that out before actually measuring," says Hori. Now the researchers from Italy, Hungary, and Germany have submerged the bizarre atoms into liquid helium and cooled it down to temperatures close to absolute zero - where the helium changes into a so-called superfluid state. An international team of scientists led by the Max Planck Institute of Quantum Optics in Garching has nevertheless combined matter and antimatter into curious hybrid atoms of helium that remain stable for short periods of time. This isolation is critically important because antimatter and matter immediately destroy each other on contact. When taking a glimpse into the shadowy world of antimatter, researchers have to rely on elaborate technical tricks to keep their samples of antimatter from coming into contact with the normal matter that surrounds us.
0 kommentar(er)
