| 释义 |
muon Nuclear Physics.|ˈmjuːɒn|
[f. mu-meson + -on1.]
A lepton that appears to be almost identical to the electron, except for being unstable and having a mass about 207 times greater, and is the chief constituent of cosmic radiation at the surface of the earth. (Orig. called a mu-meson, but now no longer classed as a meson.)
1953Sci. News Let. 3 Jan. 14/1 About 20 or so particles exist in or can be knocked out of the atoms. Some of these are well-known oldtimers, like the electron... Others are new and stranger, like the pions, the muons, the V-particles. 1958Engineering 4 Apr. 430/2 The fusion of hydrogen and deuterium (p - D reaction) catalysed by negative muons. The part played by the muon is to bind the two nuclei in a mesic molecular ion, so bringing them close enough together for fusion to occur. 1961Guardian 21 Jan. 2/4 Muons were first discovered in the naturally occurring cosmic rays and identified precisely in 1947..at Bristol University. 1968M. S. Livingston Particle Physics iv. 74 Muons are the ‘penetrating’ component of the ionizing particles in cosmic radiation observed beneath great layers of earth in salt mines. Ibid., Slow µ- muons can also displace electrons in atomic orbits and form temporarily stable atoms... Eventually, the muon decays into an electron and two neutrinos. 1968Times 28 Nov. 14/1 The muons are created by the collision of cosmic rays with matter in the upper atmosphere of the earth. 1972Nature 14 July 86/1 The mass difference of the electron and muon poses one of the inscrutable problems of particle physics. Except for the mass difference the muon does not appear to be any different from the electron. 1974Ibid. 2 Aug. 377/2 Muons are more penetrating than any other charged particles.
b. Special Comb.: muon number, a quantum number assigned to sub-atomic particles that is {pm}1 for muons and their neutrinos and 0 for other particles and is conserved in all known interactions.
1961Physical Rev. CXXIII. 1439/2 The possibility of essentially imaginary relative parities can only arise when some quantum number (here, muon number) is multiplicatively conserved. 1970D. B. Lichtenberg Unitary Symmetry i. 7 Other important symmetries are the invariances under gauge transformations. These symmetries are associated with conservation of charge Q, baryon number B, and two lepton numbers, the electron number Le and the muon number Lµ.
Hence muˈonic a., of, pertaining to, or involving a muon, or an atom having a negative muon orbiting the nucleus.
1955S. S. Schweber et al. Mesons & Fields II. 369 The same considerations lead to the conclusion that the two neutrinos ejected in µ decay are like neutrinos, even though a Dirac theory of neutrinos opens the possibility that one is an anti-neutrino... Such conclusions are important in calculating expectations for the muonic processes. 1965New Scientist 1 July 36/1 Studies of the so-called ‘muonic’ X-ray spectra do not call for high energies. 1969Sci. Jrnl. July 44/1 In a dense material, a muon is slowed down to a velocity corresponding to 1 keV in about 1 nanosecond, after which it is captured into a ‘Bohr orbit’, forming a hydrogen-like atom known as a muonic atom. 1972Physics Bull. Mar. 149/2 Muonic molecules are systems in which a negative muon binds together two nuclei. Some examples are (pµ-p)+, (pµ -d)+, and (dµ-d)+, and in practice only such ionic states are of interest. 1972Sci. Amer. Nov. 104/3 The behavior of muonic atoms has provided much information about the structure of the nucleus, particularly about the distribution of protons within nuclei. |