| 释义 |
▪ I. eta1|ˈiːtə, ˈeɪtə|
[a. Gr. ἦτα (see etacism).]
The name of the seventh letter (Η, η) of the Greek alphabet, corresponding to English e.
c1400in Mandeville Trav. (1839) iii. 20. 1642 [see upsilon 1]. 1883I. Taylor Alphabet II. vii. 85 The Latin H and the Greek eta are identical in form and in alphabetic position, though not in value.
Add:2. Particle Physics. Freq. written η. Any of a group of mesons with zero spin and isospin.
1961A. Pevsner et al. in Physical Rev. Lett. VII. 421/2 Another large peak in the 3-pion mass plot..is seen near 550 Mev, which strongly suggests the existence of a second 3-pion resonance (or particle). We shall hereafter refer to this particle as η. 1963World Bk. Year Bk. 416/2 Before the pi mesons formed, an unstable particle with a mass 1,000 times that of an electron appeared. It was called the eta meson. 1966New Statesman 8 July 51/1 The team had studied..the eta-meson. It has a very short life and decomposes into other particles, called pi-mesons. 1972G. L. Wick Elem. Particles v. 86 The omega conforms to the norms of a strongly interacting particle and decays in about 10-23 seconds. The eta, however, is a narrower resonance and takes as long as 10-18 seconds to decay. 1982Sci. Amer. Nov. 135/1 The particle decays to yield two eta mesons, which then decay to yield four photons. 1987McGraw-Hill Encycl. Sci. & Technol. (ed. 6) X. 628 An eta meson with structure (cc̄) is now known, ηc (2981), whose decay modes include ηππ, 2π+2π-, and K+K-π+π-.
▪ II. eta2|ˈiːtə|
In full, eta palm. = ita-palm.
1769E. Bancroft Ess. Nat. Hist. Guiana 61 The Eta Tree is of the same species with the foregoing [sc. cabbage tree], but smaller. 1866G. W. Bennett Illustr. Hist. Brit. Guiana 228 The Eta Palm (Mauritia flexuosa) is a beautiful tree and is adored by the Indians for the numerous uses to which it can be applied. 1922Blackw. Mag. July 6/1 The road used to end..before a great eta-palm swamp. |
