Antihydrogen spectroscopy achieved - PHYSICS

CERN physicists ended the year off right by announcing that they had analyzed the spectra of antimatter atoms for the first time.

The standard technique for atomic spectroscopy—exciting atoms with a laser and detecting the photons they emit—is unsuitable for antihydrogen. First, the coils and electrodes required to magnetically trap the antihydrogen, as shown here, leave little room for optical detectors. Second, the researchers trap only 14 antihydrogen atoms at a time, on average, so the optical signals would be undetectably weak.

Happily, antimatter offers an alternative spectroscopic method that works well for small numbers of atoms. When an antihydrogen atom is excited out of its 1S (or ground) state, it can be ionized by absorbing just one more photon. The bare antiproton, no longer confined by the magnetic field, quickly collides with the wall of the trap and annihilates, producing an easily detectable signal.

When the researchers tuned their excitation laser to the exact frequency that would excite atoms of hydrogen, about half of the antihydrogen atoms were lost from the trap during each 10-minute trial. When they detuned the laser by just 200 kHz—about 200 parts per trillion—all the antihydrogen remained in the trap. By repeating the experiment for many more laser frequencies, the ALPHA team hopes to get a detailed measurement of the transition line shape. But that will have to wait until the experiment resumes in May 2017.

Journal article :http://www.nature.com/nature/journal/vaap/ncurrent/full/nature21040.html

Story via Physics Today:http://physicstoday.scitation.org/do/10.1063/PT.5.7333/full/