| 释义 |
fine structure
[tr. G. feinstruktur (A. Sommerfeld 1916, in Ann. d. Physik LI. 2).]
1. Physics.
a. (The presence of) multiplets of closely spaced lines in atomic spectra that appear as single lines under low resolution; usu. applied to multiplets that result from the splitting of energy levels by the electron spin-orbit coupling, in contrast with hyper-fine structure.
1918Phil. Mag. Oct. 345 Here α2 is the small quantity (2πe2/hc)2, (where e is the electronic charge, h Planck's constant, and c the velocity of light) occurring again as a universal constant in the discussion of the fine structure of lines. 1936Discovery Nov. 363/1 The fine-structure of spectral lines frequently arises through the nuclei of the atoms, to which the spectrum is due, having a spin. 1942J. D. Stranathan ‘Particles’ of Mod. Physics vi. 224 The details of fine structure differ from one element to another, both as regards the number of lines in the multiplet and the spacing of these lines. 1962H. D. Bush Atomic & Nuclear Physics iii. 58 If the fine structure is examined with the aid of very high resolution instruments, each component of the fine structure is resolved into further components with separations of the order of 1 cm-1 (hyperfine structure).
b. Similar groups of lines or energies in other spectra.
1930Proc. R. Soc. A. 3 Sept. 229 To examine the fine structure of the α-rays, Rosenblum has employed the focussing method so much used in the examination of β-ray spectra. 1942J. D. Stranathan ‘Particles’ of Mod. Physics viii. 344 The previously supposed homogeneous α-rays emitted from ThC actually fall into five distinct groups. The rays are said to have a fine structure. 1955R. D. Evans Atomic Nucleus xiii. 424 Energy levels in the product nucleus determine the ‘fine structure’, or energy groups, of the reaction products.
2. gen. Small-scale variation in structure, texture, appearance, etc.
1933Nature 17 June (heading) Fine-structure of the ionosphere. 1935Discovery Apr. 108/1 This [X-ray] technique yields information on the fine-structure of bodies, of a sub-microscopic order, while the radiographic method reveals the gross structure. 1946Nature 12 Oct. 519/1 An account was given of the examination of..a cleavage face of a selenite crystal... Only low magnifications..were used, yet it was observed that the fringes were extremely ragged, indicative of a complex surface ‘fine-structure’. 1967R. Michard in J. N. Xanthakis Solar Physics v. 116 One can see that these flocculi are organized in a large cellular network..visible mainly on average-quality pictures where the fine structure is smoothed out. 1968Brit. Med. Bull. XXIV. 236/1 The fine structure of proteins has also been subjected to taxonomic analysis to estimate the relationships between the constituent amino acids. 1971Sci. Amer. July 19/1 Even more striking than the differences among the states was the shifting of populations at the county level—the changes in what might be called the fine structure of the population distribution.
3. attrib., as fine-structure constant.
1923H. L. Brose tr. Sommerfeld's Atomic Struct. & Spectral Lines viii. 497 Our representation of the L-doublet is fully determined and expressed rationally by the fine-structure constant..by the Rydberg frequency..and by the nuclear charge. 1930Ruark & Urey Atoms, Molecules & Quanta v. 134 Introducing the dimensionless fine-structure constant, α = 2πe2/hc = (7·284 {pm} 0·006) · 10-3, we get [etc.]. 1935A. S. Eddington New Pathways in Sci. xi. 234 The fine-structure constant..has reference to the structure of spectral lines, but the constant occurs more widely; just as the velocity of light occurs in many problems unconnected with optics. The fine-structure constant is really the ratio of two natural units or atoms of action. 1935S. Tolansky Fine Structure in Line Spectra and Nuclear Spin ii. 5 In general the fine structure components of a line lie very closely together. 1970Sci. Amer. Oct. 63/1 The fine-structure constant is the basic constant of quantum electrodynamics. |