Fermi
(ˈfɜːmɪ)
[The name of Enrico Fermi (1901–54), Italian-born physicist.]
1. Used attrib. to designate certain principles and concepts arising out of Fermi's work, as Fermi (coupling) constant, Fermi effect, Fermi energy, Fermi gas, Fermi interaction, Fermi level, Fermi liquid, Fermi sea; also Fermi distribution, Fermi statistics (see Fermi–Dirac); Fermi surface, a surface in momentum space representing the maximum energy, at absolute zero, of the electrons in a crystal with respect to their direction of motion.
| 1927 Sci. Abstr. A. XXX. 741 The Fermi statistics were developed for the electronic gas. 1933 Slater & Frank Introd. Theoret. Physics xli. 540 In Fig. 83..we plot the potential in which the electrons may be assumed to move. This is constant..throughout the metal, and the horizontal lines symbolize the Fermi levels, filled with electrons at the absolute zero. 1934 Chem. Abstr. XXVIII. 7148 (heading) The Fermi effect in aluminium. 1936 Mott & Sneddon Theory of Properties of Metals & Alloys ii. 53 The mean kinetic energy of the electrons will be called the ‘mean Fermi energy’. 1937 Chem. Abstr. XXXI. 3777/1 (heading) Theoretical significance of the Fermi constant. 1951 Nuovo Cimento VIII. 749 A universal Fermi interaction (that is, a direct interaction with a unique coupling constant among any four of the five particles of spin ½h, [etc.]). 1952 Proc. R. Soc. A. CCXV. 49l For the group I metals, copper, silver and gold, distortion of the Fermi surface should be small. 1953 E. Segrè Exper. Nucl. Physics II. vi. 144 The simplest of the nuclear models, that of the Fermi gas of non-interacting nucleons contained in a well of assigned diameter and depth. 1955 H. B. G. Casimir in W. Pauli Niels Bohr 119 If the behaviour of the electrons can be described by a Fermi distribution of single electron wave functions, then at the absolute zero all levels up to a certain energy ε0 will be occupied. 1955 Rev. Mod. Physics July 252/2 The introduction of the Fermi sea of electrons to rescue the relativistic theory of the electron. 1966 E. J. Konopinski Theory Beta Radioactivity iv. 103 A ‘Fermi coupling constant’, g, has been introduced here... It will measure the strength of the β-interaction. 1966 New Scientist 20 Jan. 155/1 An attempt to draw an analogy between the behaviour of liquid helium-3 at low temperatures and electrons in metals—which constitute what is called a Fermi liquid. 1970 McGraw-Hill Yearbk. Sci. & Technol. 187/1 The electronic properties of metals and degenerate semiconductors are largely determined by the behavior of electrons at and near the Fermi surface. |
2. (With lower-case initial.) A unit of length used in nuclear physics, equal to 10- 15 m.
| 1956 R. Hofstadter in Rev. Mod. Physics XXVIII. 214/2 Henceforth, we shall measure all distances in terms of 10- 13 cm as a unit and shall call this unit the fermi. For example, this formula puts the edge of the nuclear sphere of gold at a distance of 8·45 fermis from the center of the nucleus. 1965 C. M. H. Smith Textbk. Nucl. Physics ix. 263 Nuclear radii are approximately given by the formula r = 1·20 A{oneon3} fermi. 1971 Sci. Amer. July 101/3 The characteristic distance for a rho-nucleon interaction to occur in nuclear matter..is about three fermis. |