Exotic atoms

As exotic atoms are atomic similar bound particles referred to, in which at least one of the particles involved is not an ordinary atom component, so no proton , neutron , or electron .

Types

The main exotic atoms are:

Replacement of a shell electron by a negatively charged particle: ${\ displaystyle e \! \,}$ $e \! \,$
- Muonic atoms with one muon . The muon is very close to the atomic nucleus because of its high mass . Spectroscopy of muonic atoms therefore enables studies of the nuclear structure. ${\ displaystyle \ mu ^ {-} \! \,}$
- Pionic and kaonic atoms with a pion or kaon (both mesons ). The simplest example is mesonic hydrogen from a proton and a pion or kaon. Due to their even greater mass, pion and kaon are even closer to the atomic nucleus than the muon of the muonic atoms. In contrast to electrons, pions and kaons interact, since they are mesons, not only via the electromagnetic , but also via the attractive or repulsive strong interaction with the nucleons of the atomic nucleus. Parameters of this interaction can be measured on pionic and kaonic atoms. ${\ displaystyle \ pi ^ {-}}$ ${\ displaystyle K ^ {-}}$

Replacement of a proton or neutron in the atomic nucleus by another particle: ${\ displaystyle p \! \,}$ ${\ displaystyle n \! \,}$

Positronium and muonium : the atomic nucleus is replaced by a positron or an antimuon . Positronium and muonium consist exclusively of leptons . Because, according to the current state of knowledge, these are structureless, so to speak “punctiform”, positronium and muonium are particularly suitable for the highly precise investigation of the electromagnetic interaction and for measuring fundamental natural constants . ${\ displaystyle e ^ {+} \! \,}$ ${\ displaystyle \ mu ^ {+} \! \,}$

Atoms with hyper nuclei: in the atomic nucleus there are one or more hyperons .

Replacement of particles both in the shell and in the core:

Antimatter in which every atomic component is replaced by its oppositely charged antiparticle . One example is anti-hydrogen , consisting of an antiproton in the nucleus and a positron in the shell.
Muonic, pionic, kaonic and protonic antimatter : Antimatter in which a shell positron is also replaced by a positively charged anti-muon , pion , kaon or a proton. ${\ displaystyle \ mu ^ {+} \! \,}$ ${\ displaystyle \ pi ^ {+} \! \,}$ ${\ displaystyle K ^ {+} \! \,}$
Atoms from two mesons, especially from two pions or one pion and one kaon

properties

With the exception of the anti-atoms, such as the anti-hydrogen atom, all of the exotic atoms mentioned are unstable and short-lived. Antiatoms are also only stable as long as they do not come into contact with ordinary matter, otherwise they will annihilate ( annihilation ).

Occurrence

Positronium, muonium and muonic atoms occur naturally in very small quantities as secondary products of cosmic radiation , as do pionic or kaonic atoms, which, however, live much shorter. On earth, the exotic atoms, including anti-hydrogen atoms, can be generated using particle accelerators with sufficiently high beam energy.

exploration

The investigation of anti-hydrogen atoms in the European research center CERN is intended to prepare a precise test of the symmetry of matter and antimatter. Such experiments with higher accuracy are planned at the GSI Helmholtz Center for Heavy Ion Research in Darmstadt.

swell

Rudolf Gross: Physik IV, lecture notes SS 2003 (PDF 1.52 MB) March 2003, accessed on December 13, 2009 .

Web links

Paul Kienle , Stefan Meyer: Exotic Atoms: Roses from the flower garden of subatomic physics. (pdf; 3.2 MB) Austrian Academy of Sciences, accessed on July 8, 2016 (presentation slides).
Exotic atoms. In: LEIFIphysik. Joachim Herz Foundation LEIFI , June 19, 2018, accessed on June 19, 2018 .