emission
(ɪˈmɪʃən)
[ad. L. ēmissiōn-em, n. of action f. ēmittĕre to emit.]
The action of the vb. emit.
† 1. The action of sending forth. Obs. in gen. sense.
| 1607 Topsell Four-f. Beasts (1673) 181 Emission or sending away. 1646 Sir T. Browne Pseud. Ep. (L.), Populosity..requireth..emission of colonies. 1657 Hobbes Absurd Geom. Wks. 1845 VII. 398 The authority..of the Apostles in the emission of preachers to the infidels. 1827 G. S. Faber Origin of Expiatory Sacrifice 197, note, Noah seems to have twice selected that holyday for the emission of the dove. |
† 2. The issuing, publication (of a book, a notice).
| 1751 Johnson Rambl. No. 169 ¶11 The tardy emission of Pope's compositions. 1779 Johnson Life Pope Wks. IV. 40 The emission..of the Proposals for the Iliad. |
3. The issuing or setting in circulation (bills, notes, shares, etc.). Also
concr.| 1773 Gentl. Mag. XLIII. 295 All the emissions of their paper-currency..are forged. 1790 Burke Fr. Rev. Wks. V. 415 Proposing the emission of assignats. 1865 H. Phillips Amer. Paper Curr. II. 36 A subsequent emission of bills of credit. |
4. a. The action of giving off or sending out (chiefly what is subtle or imponderable, light, heat, gases, odours, sounds, etc.).
† Formerly also the sending forth (of the soul) in death; the allowing ‘the animal spirits’ to escape; and
fig. the ‘pouring out’, ‘breathing forth’ (of affection, etc.).
| a 1619 Donne Biathan. (1644) 190 This actuall emission of his soule, which is death. a 1626 Bacon (L.), Tickling causeth laughter: the cause may be the emission of the spirits. 1660 Jer. Taylor Duct. Dubit. i. iv. Wks. IX. 161 The voice was..effective..in the direct emission. 1693 South Serm. (L.), Affection flamed up in collateral emissions of charity to its neighbour. 1751 Johnson Rambl. No. 146 ¶9 Growing fainter..at a greater distance from the first emission. 1833 Sir J. Herschel Astron. x. 311 The tail of the..comet..occupied only two days in its emission from the comet's body. 1853 ― Pop. Lect. Sc. i. §35. (1873) 26 Puffs of smoke, at every moment of their emission from the crater. 1859 G. Wilson Gateways Knowl. (ed. 3) 77 The emission of fragrance. 1871 Blackie Four Phases i. 71 The emission of sparks of light. |
b. Optics.
theory of emission = emission theory, sense 7 below.
| 1831 Brewster Optics xv. §94. 134 The Newtonian theory of light, or the theory of emission. |
c. Physics. The action of giving off radiation or particles; a flow of electrons from a cathode-ray tube or other source.
| 1900 Rutherford in Phil. Mag. XLIX. 12 The results seem to point to a uniform rate of emission of the emanation at all pressures. 1955 W. Heisenberg in W. Pauli Niels Bohr 25 Let a measuring apparatus be placed in the neighbourhood, which registers the emission of an electron. 1955 Sci. Amer. June 40/3 It is from these bursts of emission that radio astronomers have obtained most of their new information about the Sun's activities. |
5. concr. That which is emitted; an emanation, effluvium.
| 1664 Power Exp. Philos. iii. 155 The Magnetical Emissions..are..Corporeal Atoms. 1664 Evelyn Kal. Hort. (1729) 218 Warm and benign Emissions of the Sun. 1871 Tyndall Fragm. Sc. (ed. 6) I. ii. 43 We obtain the value of the purely luminous emission. |
6. Phys. = L.
emissio seminis.
| 1646 Sir T. Browne Pseud. Ep. 371 There is no generation without a joynt emission. 1665 Glanvill Sceps. Sci. The other Instances of..Emissions. 1885 Law Reports Appeal Cases X. 176. |
7. emission nebula Astr., a nebula which shines with its own light, produced inside it;
emission spectrum, a spectrum which shows the radiations from an emitting source;
emission theory, any theory of light or other radiation according to which it consists of streams of particles rather than waves.
| [1954 Physics Abstr. LVII. 1018/2 Two fundamental types of nebulae follow from this discussion: (1) the emission-type nebulae, consisting of atomic and ionized H, without dust, and (2) dark nebulae, with dust, consisting mainly of H2.] 1956 Austral. Jrnl. Physics IX. 227 Ordinary *emission nebulae emit radio waves as the result of their high electron temperature by the process of free-free transitions. 1974 Sci. Amer. Oct. 34/3 These reflection nebulas are useful for studying the properties of the interstellar dust grains, but they are distinguished from the true emission nebulas, which shine as a result of the atomic processes going on within them. 1978 Pasachoff & Kutner University Astron. xxiii. 573 The Great Nebula of Orion..is an emission nebula. |
| 1888 Phil. Mag. 5th Ser. XXVI. 289 Ångström thought it improbable that oxygen should have a spectrum of such a character, since he failed to obtain an *emission spectrum resembling it. 1930 G. Thomson Atom ii. 22 It is from the position of these black lines (Fraunhofer lines) that the nature of the substances present in the sun has been found. Such a black line spectrum is called an ‘absorption’ spectrum, in contrast to the bright line ‘emission’ spectrum. 1962 Listener 31 May 949/2 Surrounding the Sun is a layer made up of tenuous gas, which, if seen on its own, would produce an emission spectrum made up of isolated bright lines. |
| 1880 Bastian Brain 62 An *emission theory..will not hold for the diffusion of light. 1926 R. W. Lawson tr. Hevesy & Paneth's Man. Radioactivity i. 5 Finally for cathode rays the emission theory, and for Röntgen rays the wave theory held the field. |