Because these substitute particles are usually unstable, exotic atoms typically have very short lifetimes.

However, none of these processes produces the types of exotic atoms described by futurists.

Protonium is an exotic atom in which a proton and an antiproton orbit each other.

The tau lepton is predicted to form exotic atoms like other charged subatomic particles.

What is called "true muonium", a bound state of a muon and an antimuon, is a theoretical exotic atom which has never been observed.

Kaonic hydrogen is an exotic atom consisting of a negatively charged kaon orbiting a proton.

Positronium is a type of exotic atom that is made of one positron and one electron.

Positronium (Ps) is a system consisting of an electron and its anti-particle, a positron, bound together into an "exotic atom".

An exotic atom is an otherwise normal atom in which one or more sub-atomic particles have been replaced by other particles of the same charge.

Other exotic atoms have been created by replacing one of the protons, neutrons or electrons with other particles that have the same charge.

However, since 5 July 2010, an international research team has been able to make measurements involving an exotic atom made of a proton and a negatively-charged muon.

Experimental observation of the decay rates of muons bound in exotic atoms has shown, however, that ground state electrons are in fact in motion.

The wavefunction of the bound state is said to be hydrogenic, an exotic atom state akin to that of a hydrogen atom.

The concepts of the Rydberg formula can be applied to any system with a single particle orbiting a nucleus, for example a He ion or a muonium exotic atom.

A positive muon, when stopped in ordinary matter, can also bind an electron and form an exotic atom known as muonium (Mu) atom, in which the muon acts as the nucleus.

The true analogs of positronium in the theory of strong interactions, however, are not exotic atoms but certain mesons, the quarkonium states, which are made of a heavy quark such as the charm or bottom quark and its antiquark.

Picotechnology was described as involving the alteration of the structure and chemical properties of individual atoms, typically through the manipulation of energy states of electrons within an atom to produce metastable (or otherwise stabilized) states with unusual properties, producing some form of exotic atom.