| 释义 |
ion Electr.|ˈaɪən|
[a. Gr. ἰόν, neut. pr. pple. of ἰέναι to go.]
1. Name given by Faraday to either of the constituents which pass to the ‘poles’ or electrodes in electrolysis: the general term including anion and cation. In modern use, any individual atom, molecule, or group having a net electric charge (either positive or negative), whether in an electrolytic solution or not.
1834W. Whewell Let. to Faraday 5 May in I. Todhunter William Whewell (1876) II. 182 For the two together you might use the term ions. 1834Faraday in Phil. Trans. R. Soc. CXXIV. 79 Finally, I require a term to express those bodies which can pass to the electrodes... I propose to distinguish these bodies by calling those anions which go to the anode of the decomposing body; and those passing to the cathode, cations; and when I have occasion to speak of these together, I shall call them ions. [Note] Since this paper was read, I have changed some of the terms which were first proposed. Ibid. 112 A body decomposable directly by the electric current, i.e. an electrolyte, must consist of two ions. Ibid., Compound ions are not necessarily composed of electro-chemical equivalents of simple ions. For instance, sulphuric acid, boracic acid, phosphoric acid, are ions, but not electrolytes, i.e. not composed of electro-chemical equivalents of simple ions. 1856W. A. Miller Elem. Chem. II. xviii. 1110 When a binary compound, such as a fused chloride,..is submitted to electrolysis, the ions or components of the compound are separated at the respective electrodes in equivalent proportions. 1870R. M. Ferguson Electr. 161 The constituents into which the electrolyte is decomposed are called ions. 1879Encycl. Brit. VIII. 107/1 Sodium acetate and silver chloride are therefore electrolytes of which Ag, Cl, Na, C2H3O2 are the respective ions. 1896W. R. Whitney tr. Le Blanc's Elem. Electrochem. iii. 60 Only those substances conduct which are at least partly dissociated, and therefore the conductivity is due to the dissociated parts; to the latter, which were called by him the ‘ions’, Arrhenius ascribed electric charges. 1896Rutherford & Thomson in Phil. Mag. XLII. 405 We have made..experiments with the view to seeing whether there is any polarization when a current of electricity passes through a gas; we have not, however, been able to satisfy ourselves of the existence of this effect. The absence of polarization implies, however, that the ions are able to give up their charges to the metal electrodes. 1899Rutherford in Ibid. XLVII. 112 The theory has been put forward that the rays in passing through the gas produce positively and negatively charged particles in the gas, and that the number produced per second depends on the intensity of the radiation and the pressure... The term ion was given to them from analogy with electrolytic conduction, but in using the term it is not assumed that the ion is necessarily of atomic dimensions; it may be a multiple or submultiple of the atom. 1927N. V. Sidgwick Electronic Theory of Valency vi. 91 In a crystal like calcium carbonate we find the same kind of relation between the calcium ion and the CO3 ion, but a different one for the constituent atoms of the CO3 group;..this may be taken as evidence that the calcium and the CO3 are themselves ions, but that the atoms of the CO3 group are covalently linked to one another. 1962P. J. & B. Durrant Introd. Adv. Inorg. Chem. xii. 346 An ionic crystal is one in which the units of crystal structure are the ions of a salt. 1967New Scientist 30 Nov. 531/1 The normal electrode separation is less than 1 mm, so there is a very strong electric field which ionizes the gas atoms, giving ions and electrons.
2. Special Comb.: ion beam, a current of ions moving in a fixed direction; ion bombardment, the process of bombarding a surface with ions (usu. of an inert gas), so breaking up the surface, used to remove impurities; hence ion-bombarded a.; ion burn, the damaging of the phosphor of a cathode-ray tube by negatively ionized gas molecules produced by the electron beam and focused on to the screen; also, an ion spot so produced; ion chamber, an ionization chamber; ion drive, (a) = ion propulsion; (b) = ion engine; ion engine, a rocket engine that employs ion propulsion; ion etching, the controlled removal of extremely thin layers of material from the surface of an object by the use of an ion beam; ion gun, a device in which ions are produced (usu. by the ionization of a gas) and emitted in a beam; ion implantation, the implantation of ions in a crystalline material (see implantation 7); ion pair, (a) a pair of oppositely charged ions held together in a solution by electrostatic attraction; (b) a negative ion (or an electron) and a positive ion formed from a neutral atom or molecule by the action of radiation; ion propulsion, a mode of rocket propulsion in which thrust is produced by the ejection of ions produced inside the engine and accelerated by an electric field; ion rocket, (a) = ion engine; (b) a rocket in which an ion engine is the means of propulsion; ion source, a device for producing ions, spec. an ion gun; ion spot, (a) a dark spot in the middle of the screen of a cathode-ray tube where the phosphor is damaged as a result of ion burn; (b) a white spot in a television picture produced as a spurious signal when ionized gas molecules strike the target of a television camera tube; ion trap, a device designed to catch ions; spec. one in a cathode-ray tube or television camera tube that prevents ionized molecules from reaching the screen or the target and causing an ion spot. Also ion exchange.
1932Physical Rev. XL. 33 Intense high speed ion beams. 1951Jrnl. Brit. Interplanetary Soc. X. 253 The acceleration of a space ship by an ion beem seems to offer no particular difficulties. 1970New Scientist 5 Feb. 256/1 The ion beam, projected at a small area of the sample, consists of heavy, positively charged ions of inert gas, which remove atoms from the specimen's surface layers.
1959Jrnl. Chem. Physics XXX. 926/2 The relative ease of removal of oxygen can therefore not be explained by the assumption that the ion-bombarded and annealed surface is partially oxygen contaminated.
1930Rev. Mod. Physics II. 186 ‘Sputtering’, or disintegration of an electrode subjected to positive ion bombardment is a well known and often troublesome phenomenon. 1952Trans. Faraday Soc. XLVIII. 747 As a general procedure for cleaning surfaces, the inert gas ion-bombardment has some advantages: its main disadvantage is that there is sputtering of the metal on to the walls of the vessel. 1960Jrnl. Appl. Physics XXXI. 1516 (title) Ion-bombardment etching of synthetic fibers.
1954E. Molloy Radio & Television Engineers' Ref. Bk. xxiv. 27 The third technique of preventing ion burn is by protecting the screen with a layer of aluminium. 1956[see ion spot below]. 1963J. R. Davies Understanding Television ii. 62 Ion burns normally show up as brown circles an inch or so in diameter, the discoloration being greatest at the centre of the burn. In some cathode ray tubes, protection against ion burn is achieved by mounting part of the electron gun assembly at an angle, and..applying across the tube neck a fixed magnetic field which causes electrons only to be deflected across the screen.
1955Bull. Atomic Sci. June 213/3 An ion chamber, however, is a device which directly measures the dose to the air volume it encloses. 1962F. I. Ordway et al. Basic Astronautics iv. 121 Solar radiation intensities in the Lyman-alpha experiment were measured by a photo-sensitive ion chamber.
1958C. C. Adams et al. Space Flight xiv. 346 Both rubidium and cesium have been considered as the propellant for the ion drive. 1960Aeroplane XCVIII. 776/2 Ion-drive cannot be used in propelling space-vehicles from the Earth's surface because of their inherently low thrust. 1962F. I. Ordway et al. Basic Astronautics x. 424 The three basic elements of the ion drive are the emitter, the accelerator, and the beam neutralizer.
1960Aeroplane XCVIII. 776/2 (heading) Experimental ion engine. 1961[see ion rocket below]. 1971Jrnl. Brit. Interplanetary Soc. XXIV. 573 The use of pulsed plasma thrusters rather than ion engines for attitude control has..become a distinct possibility.
1965Chem. Abstr. LXII. 3491 (heading) Ion etching: an effective method for the elimination of foreign layers in ultra vacuum. 1968Times 13 Nov. 16/1 The inside appearance of a red blood cell has been revealed for the first time by the novel combination of two physical techniques, scanning electron microscopy and ion etching... Ion etching has so far been used chiefly to study the structure of metals. The specimen is bombarded with a stream of high energy ions and the inner structure of the material is revealed as successive layers are stripped off. 1970New Scientist 5 Feb. 256/2 It has been possible to use ion etching to penetrate the cuticular layers of insects.
1952Jrnl. Brit. Interplanetary Society XI. 179 Any rocket system requiring the conversion of electric to kinetic energy will require one or more ion guns. 1957Physical Rev. CVII. 642/1 The performance of the spectrometers was tested with an electron gun and with an ion gun. 1967New Scientist 30 Nov. 531/1 The apparatus..consists of two ion sources (ion guns) which direct beams of ions at shallow angles on to the centres of the faces of a disc-like sample of ceramic.
1965Nuclear Instruments & Methods XXXVIII. 169 (heading) Doping of silicon by ion implantation. 1970Times 23 Jan. 27/8 This makes a low-temperature method of doping the silicon, such as ion implantation, an attractive approach to..flexible circuit fabrication. 1970New Scientist 15 Oct. Suppl. 16/1 In ion implantation, the necessary impurities are accelerated by an electric field to an energy sufficient to embed them into the silicon to the depth required. 1972Physics Bull. Oct. 612/3 Ion implantation can be helpful in understanding already known damage centres by careful choice of bombarding isotope.
1933Jrnl. Amer. Chem. Soc. LV. 477 The changes in the properties of the solvent..caused by the presence of undissociated (non-conducting) ion pairs will be neglected. 1941Proc. 7th Internat. Congr. Genetics 246 At 0·01 r. per min. there is on the average only one ion pair produced in a sperm nucleus every 27 min. and since the ion pairs produced by γ-rays are rather far apart, it is now more difficult than ever to avoid the conclusion that individual mutations arise from individual ionizations and that there is no threshold intensity. 1963B. Fozard Instrumentation Nucl. Reactors ii. 13 When a charged particle of high energy is introduced into the sensitive volume of a gas ionisation detector it undergoes large numbers of ionising and exciting collisions... In suitable conditions the whole of this energy is expended within the sensitive volume. In such cases the total number of ion pairs produced is a direct measure of the particle energy. 1964Black & Wagner Dynamic Path. xi. 231 The different types of ionizing radiation produce the same fundamental change in matter, that is, the ejection of planetary electrons from atoms or molecules, leading to the formation of ion pairs.
1957Jrnl. Brit. Interplanetary Soc. XVI. 233 A system which may ultimately utilize power from fusion is that of ion (or plasma) propulsion. Ibid., Much serious attention is being given to the ion-propulsion problem in the U.S.A. 1966McGraw-Hill Encycl. Sci. & Technol. VII. 245/2 The space charge represents one of the serious obstacles of any ion-propulsion system.
1949Jrnl. Brit. Interplanetary Soc. VIII. 64 These techniques form the basis for what we shall here call the ‘ion rocket’, the jet of which might more correctly be termed an exhaust beam. 1951Ibid. X. 248 The use of ion rockets as a means for propelling vehicles between satellite stations. 1953Ann. Reg. 1952 406 The ‘most feasible project’ was described as consisting of space stations circling the most important planets with ion rockets plying between them. 1961Flight LXXIX. 330/2 The earliest ion rockets to be considered for spaceflight will have a thrust of one-tenth of a pound and will be powered by 30kW SNAP-8 nuclear reactors after first⁓stage launch by Atlas-Centaur or Saturn C-1 boosters. Higher-powered ion engines (up to one megawatt) will also be considered. 1971Nature 6 Aug. 357/1 What was called space technology—the design and operation of solar cells, ion rockets and the like.
1955Gloss. Terms Radiology (B.S.I.) 43 Ion source, a device in which gas ions are produced, focused and accelerated, and emitted as a narrow beam. 1966McGraw-Hill Encycl. Sci. & Technol. VII. 245/1 The ionizer or ion source converts the propellant from its original stored form to a system of charged corpuscles. 1967Ion source [see ion gun above].
1940D. G. Fink Princ. Television Engin. viii. 341 If magneto-static focusing is used, the ion spot is spread over a much larger area (often the full area of the screen) and is much less troublesome, whether electric or magnetic deflection is used. 1953Amos & Birkinshaw Television Engin. I. v. 93 Spurious signals in the form of a white ion spot are eliminated by use of an ion-trap mesh situated close to the target. 1953H. A. Chinn Television Broadcasting ii. 69 Occasionally, a white spot..may be observed in the center of the picture. Such a spot, especially if it is visible on the monitor with the camera lens capped, is probably an ion spot. 1956M. Slurzberg et al. Essent. Television x. 375 A concentrated bombardment of the fluorescent screen by the heavy ions produces a small brown circle in the centre of the picture screen, called an ion burn or ion spot.
1905Bragg & Kleeman in Phil. Mag. X. 321 An arrangement which we find to be of great importance is the ion-trap which is placed under the gauze of the ionization chamber. 1940D. G. Fink Princ. Television Engin. viii. 342 The ion spot may..be eliminated by an ingenious construction in the electron gun known as an ‘ion trap’. 1953Ion-trap [see ion spot above]. 1954E. Molloy Radio & Television Engineers' Ref. Bk. xxiv. 27 The successful operation of..ion traps depends upon the different paths followed by the electrons and negative ions under the action of magnetic fields. 1967Wharton & Howorth Princ. Television Reception iv. 59 A small permanent magnet known as the ion trap magnet was mounted on the neck of the tube to deflect the electrons so that they travelled axially and landed on the screen. |