Exotic Atom - Hadronic Atoms

Hadronic Atoms

A hadronic atom is an atom in which one or more of the orbital electrons is replaced by a charged hadron. Possible hadrons include mesons such as the pion or kaon, yielding a mesonic atom; antiprotons, yielding an antiprotonic atom; and the Σ− particle, yielding a Σ− or sigmaonic atom.

Unlike leptons, hadrons can interact via the strong force, so the energy levels of hadronic atoms are influenced by nuclear forces between the nucleus and the hadron. Since the strong force is a short-range interaction, these effects are strongest if the atomic orbital involved is close to the nucleus, when the energy levels involved may broaden or disappear because of the absorption of the hadron by the nucleus. Hadronic atoms, such as pionic hydrogen and kaonic hydrogen, thus provide interesting experimental probes of the theory of strong interactions, quantum chromodynamics.