Muonium

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Simplified representation of the muonium.

Myonium ( English muonium ) is an exotic atom made up of an anti- muon and an electron . The anti-muon, a muon with a positive elementary charge , has a lifespan of about 2 µs and is the representative of the proton in comparison to a normal hydrogen atom . This exotic atom is one of the most fundamental systems in atomic physics . The muonium atom behaves chemically like hydrogen, thus providing a lighter by a factor of nine hydrogen isotope . It was founded in 1960 by Vernon Hughes discovered and employees.

Precise spectroscopic measurements on the atom have led to very precise values ​​for fundamental natural constants such as the mass of the muon, the magnetic moment of the muon and the coupling constant of the electromagnetic interaction , the Sommerfeld fine structure constants . The accuracy of the theoretical description of muonium far exceeds that which is possible for ordinary hydrogen, since the atomic system consists solely of leptons , which can be regarded as point-like . Measurements on the muonium atom are therefore far superior to those on natural hydrogen with regard to the informative value of fundamental forces in physics , although some of them are possible with higher technical accuracy.

Furthermore, the atom was used for a precise test of the conservation of the charged lepton number ; one of the great unsolved mysteries of modern physics. The hypothetical spontaneous decay of muonium into its anti-atom antimyonium was first discussed by B. Pontecorvo and theoretically investigated in detail by Feinberg and Weinberg in 1961. The Swiss Paul Scherrer Institute (PSI) looked for spontaneous transitions from the atom muonium to its anti-atom antimyonium. An upper bound for the coupling strength of the (still hypothetical) conversion process was found: where the Fermi coupling constant is the weak interaction . This meant that a large number of speculative theories beyond the standard model could be excluded. Improved experiments are in preparation. Another application of the atom was an extremely precise test of CPT symmetry and Lorentz invariance .

The muonium atom is also used in the study of condensed matter . Here it is often viewed as a light isotope of hydrogen, with which u. a. Have the diffusion properties of hydrogen in materials and magnetic properties of materials investigated. The dynamics of chemical processes can also be studied with it.

The muonium atom is fundamentally different from muonic atoms , in which an electron is replaced by a negative muon.

literature

  • Klaus P. Jungmann: Precision Muonium Spectroscopy . In: J. Phys. Soc. Jpn. tape 85 , 2016, p. 091004 , doi : 10.7566 / JPSJ.85.091004 , arxiv : 1603.01195 (English).
  • L. Willmann, K. Jungmann: The Muonium Atom as a Probe of Physics beyond the Standard Model . In: Lect. Notes Phys. tape 499 , 1997, pp. 43–56 , doi : 10.1007 / BFb0104314 , arxiv : hep-ex / 9805013 (English).
  • Gisbert zu Putlitz: Exotic Atoms . In: Lexicon of Physics . Spectrum of Science, Heidelberg 1998 ( Spektrum.de ).
  • Sherman Frankel: Rare and Ultra-rare Muon decays . In: VW Hughes, CS Wu (Ed.): Myon Physics. Vol II. Weak Interactions . Academic Press, 1975, ISBN 0-12-360602-0 , pp. 83–113 , 105f (English, google.es ).

Footnotes

  1. ^ A b Klaus P. Jungmann: Past, Present and Future of Muonium . In: In Memory of Vernon Willard Hughes . S. 134–153 , doi : 10.1142 / 9789812702425_0009 , arxiv : nucl-ex / 0404013 (English).
  2. ^ Hydrogen - High Precision Measurements for Fundamental Physics. In: mpq.mpg.de. Retrieved February 3, 2018 .
  3. ↑ B. Pontecorvo: Mesonium and Antiesonium . In: Zhur. Eksp. i Teoret. Fiz. tape 33 , 1957, pp. 549 (Russian, English translation: Soviet Phys.-JETP 6 (33), 429 (1958) [PDF]).
  4. ^ G. Feinberg, S. Weinberg: Conversion of Muonium into Antimuonium . In: Phys. Rev. Band 123 , 1961, pp. 1439 , doi : 10.1103 / PhysRev.123.1439 .
  5. ↑ W. Bertl: Muonium Antimuonium conversion experiment. MMbar Collaboration, PSI, April 4, 2002, archived from the original on April 4, 2005 (English).;
  6. ↑ M. Aoki: Prospects of muonium to antimuonium conversion and μ −– μ + conversion at PRISM . In: Nucl. Instrum. Meth. A . tape 503 , no. 1–2 , 2003, pp. 258-261 , doi : 10.1016 / S0168-9002 (03) 00689-2 ( preprint [PDF]).
  7. ^ VW Hughes, M. Grosse Perdekamp, ​​D. Kawall and W. Liu, K. Jungmann, G. zu Putlitz: Test of CPT and Lorentz Invariance from Muonium Spectroscopy . In: Phys. Rev. Lett . tape 87 , 2001, p. 111804 , doi : 10.1103 / PhysRevLett.87.111804 , arxiv : hep-ex / 0106103 (English).
  8. ↑ Bulk µSR Facility. Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, archived from the original on October 9, 2007 .;
  9. ↑ Myonic Atoms, Exotic Atoms ( Memento of the original from April 12, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. ( LEIFI ) @1@ 2Template: Webachiv / IABot / www.leifiphysik.de