Muonium is an exotic atom made up of an antimuon and an electron,[1] which was discovered in 1960 by Vernon W. Hughes [2] and is given the chemical symbol Mu. During the muon's 2.2 µs lifetime, muonium can enter into compounds such as muonium chloride (MuCl) or sodium muonide (NaMu). Due to the mass difference between the antimuon and the electron, muonium (μ+ e−) is more similar to atomic hydrogen ( p+e−) than positronium (e+e−). Its Bohr radius and ionization energy are within 0.5% of hydrogen, deuterium, and tritium, and thus it can usefully be considered as an exotic light isotope of hydrogen.[3]
Although muonium is short-lived, physical chemists study it using muon spin spectroscopy (μSR),[4] a magnetic resonance technique analogous to nuclear magnetic resonance (NMR) or electron spin resonance (ESR) spectroscopy. Like ESR, μSR is useful for the analysis of chemical transformations and the structure of compounds with novel or potentially valuable electronic properties. Muonium is usually studied by muon spin rotation, in which the Mu atom's spin precesses in a magnetic field applied transverse to the muon spin direction (since muons are typically produced in a spin-polarized state from the decay of pions), and by avoided level crossing (ALC), which is also called level crossing resonance (LCR).[4] The latter employs a magnetic field applied longitudinally to the polarization direction, and monitors the relaxation of muon spins caused by "flip/flop" transitions with other magnetic nuclei.
Because the muon is a lepton, the atomic energy levels of muonium can be calculated with great precision from quantum electrodynamics (QED), unlike in the case of hydrogen, where the precision is limited by uncertainties related to the internal structure of the proton. For this reason, muonium is an ideal system for studying bound-state QED and also for searching for physics beyond the standard model.[5]
Nomenclature
Normally in the nomenclature of particle physics, an atom composed of a positively charged particle bound to an electron is named after the positive particle with "-ium" appended, in this case "muium". The suffix "-onium" is mostly used for bound states of a particle with its own antiparticle. The exotic atom consisting of a muon and an antimuon is known as "true muonium". It is yet to be observed, but it may have been generated in the collision of electron and positron beams.[6][7]
References
IUPAC (1997). "Muonium". In A.D. McNaught, A. Wilkinson (ed.). Compendium of Chemical Terminology (2nd ed.). Blackwell Scientific Publications. doi:10.1351/goldbook.M04069. ISBN 978-0-86542-684-9.
V.W Hughes; et al. (1960). "Formation of Muonium and Observation of its Larmor Precession". Physical Review Letters. 5 (2): 63–65. Bibcode:1960PhRvL...5...63H. doi:10.1103/PhysRevLett.5.63.
Walker, David C (1983-09-08). Muon and Muonium Chemistry. p. 4. ISBN 978-0-521-24241-7.
J.H. Brewer (1994). "Muon Spin Rotation/Relaxation/Resonance". Encyclopedia of Applied Physics. 11: 23–53.
K.P. Jungmann (2004). "Past, Present and Future of Muonium". Proceedings of the Memorial Symposium in Honor of Vernon Willard Hughes, New Haven, Connecticut, 14–15 Nov 2003: 134–153.arXiv:nucl-ex/0404013. Bibcode:2004shvw.conf..134J. CiteSeerX 10.1.1.261.4459. doi:10.1142/9789812702425_0009. ISBN 978-981-256-050-6.
S.J. Brodsky, R.F. Lebed (2009). "Production of the smallest QED atom: True muonium (µ⁺µ⁻)". Physical Review Letters. 102 (21): 213401.arXiv:0904.2225. Bibcode:2009PhRvL.102u3401B. doi:10.1103/PhysRevLett.102.213401. PMID 19519103.
H. Lamm, R.F. Lebed (2013). "True Muonium (µ⁺µ⁻) on the Light Front: A Toy Model".arXiv:1311.3245 [hep-ph].
vte
Particles in physics
Elementary
Fermions
Quarks
Up (quark antiquark) Down (quark antiquark) Charm (quark antiquark) Strange (quark antiquark) Top (quark antiquark) Bottom (quark antiquark)
Leptons
Electron Positron Muon Antimuon Tau Antitau Electron neutrino Electron antineutrino Muon neutrino Muon antineutrino Tau neutrino Tau antineutrino
Bosons
Gauge
Scalar
Hypothetical
Superpartners
Gauginos
Others
Axino Chargino Higgsino Neutralino Sfermion (Stop squark)
Others
Axion Curvaton Dilaton Dual graviton Graviphoton Graviton Inflaton Leptoquark Magnetic monopole Majoron Majorana fermion Dark photon Planck particle Preon Sterile neutrino Tachyon W′ and Z′ bosons X and Y bosons
Composite
Hadrons
Baryons
Nucleon
Proton Antiproton Neutron Antineutron Delta baryon Lambda baryon Sigma baryon Xi baryon Omega baryon
Mesons
Pion Rho meson Eta and eta prime mesons Phi meson J/psi meson Omega meson Upsilon meson Kaon B meson D meson Quarkonium
Exotic hadrons
Others
Atomic nuclei Atoms Exotic atoms
Positronium Muonium Tauonium Onia Pionium Superatoms Molecules
Hypothetical
Baryons
Hexaquark Heptaquark Skyrmion
Mesons
Others
Mesonic molecule Pomeron Diquark R-hadron
Anyon Davydov soliton Dropleton Exciton Hole Magnon Phonon Plasmaron Plasmon Polariton Polaron Roton Trion
Lists
Baryons Mesons Particles Quasiparticles Timeline of particle discoveries
Related
History of subatomic physics
timeline Standard Model
mathematical formulation Subatomic particles Particles Antiparticles Nuclear physics Eightfold way
Quark model Exotic matter Massless particle Relativistic particle Virtual particle Wave–particle duality Particle chauvinism
Wikipedia books
Hadronic Matter Particles of the Standard Model Leptons Quarks
Hellenica World - Scientific Library
Retrieved from "http://en.wikipedia.org/"
All text is available under the terms of the GNU Free Documentation License
