antiatoms

Antiatoms are the antimatter counterparts of ordinary atoms. They are bound states of antiparticles with the same masses as their matter equivalents but opposite charges and quantum numbers. The best known example is antihydrogen, consisting of an antiproton nucleus and a positron orbiting it. Other antiatoms include antihelium and more exotic species created in laboratory environments.

Production and trapping of antiatoms occur in high-energy physics facilities. Antiprotons and positrons are generated, cooled, and stored in electromagnetic traps. By mixing these antiparticles in nested Penning traps, researchers synthesize neutral antihydrogen atoms. Because antihydrogen is electrically neutral, it can be confined with magnetic minimum traps, enabling longer observation times for precise measurements of spectra and for experiments testing gravity on antimatter.

Experiments and findings have demonstrated the creation of trapped antihydrogen and its use in spectroscopy and fundamental tests. Spectroscopic measurements of antihydrogen, such as transitions analogous to those in hydrogen, are compared with hydrogen to test CPT symmetry. Other efforts aim to determine how antimatter responds to gravity to test the equivalence principle for antimatter. In addition, searches for antihelium in cosmic rays and laboratory settings continue to constrain possible antimatter abundances. Antiatoms annihilate on contact with ordinary matter, producing detectable radiation, which is exploited both for detection and as a practical challenge for containment.

Significance lies in tests of fundamental symmetries and interactions, constraints on antimatter gravity, and implications for understanding the matter–antimatter asymmetry of the universe. While antiatoms have been produced and studied in controlled experiments, they remain challenging to study in large quantities, and no deviations from established physics have been observed within current experimental limits.