| spontaneous emission | <radiobiology> Radiation randomly emitted by excited atoms or ions. Contrast with stimulated emission. (09 Oct 1997) |
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| stimulated emission | <radiobiology> Radiation coherently emitted by excited ions when driven by a passing light wave and the appropriate transition wavelength. Laser means Light Amplification by Stimulated Emission of Radiation, it occurs when there is a population inversion between the upper and lower energy states of the transition, such that stimulated emission can dominate excitation. Stimulated emission is coherent and codirectional with the stimulating wave, and the rate of stimulated emission is proportional to the intensity of the stimulating wave. (09 Oct 1997) |
| ion cyclotron emission | <radiobiology> As ions gyrate around in a magnetic field (see also larmor radius or cyclotron radius), they radiate radio-frequency electromagnetic waves. This is known as ion cyclotron emission, and can be measured to help diagnose a plasma. (09 Oct 1997) |
| electron cyclotron emission | <physics, radiobiology> As electrons gyrate around in a magnetic field (see also larmor radius or cyclotron radius), they radiate radio-frequency electromagnetic waves. This is known as electron cyclotron emission, and can be measured to help diagnose a plasma. (09 Oct 1997) |
| emission | 1. The act of sending or throwing out; the act of sending forth or putting into circulation; issue; as, the emission of light from the sun; the emission of heat from a fire; the emission of bank notes. 2. That which is sent out, issued, or put in circulation at one time; issue; as, the emission was mostly blood. 3. <physics> Emission theory, the theory of Newton, regarding light as consisting of emitted particles or corpuscles. See Corpuscular theory. Origin: L. Emissio: cf. F. Emission. Source: Websters Dictionary (01 Mar 1998) |
| emission-computed tomography | <radiology> Tomography using emissions from radionuclides and a computer algorithm to reconstruct the image. (20 Jun 2000) |
| emission electron | <physics>? A beta particle resulting from radioactive decay. (05 Mar 2000) |
| emission offset | <chest medicine> A reduction in the air pollution emissions of existing sources to compensate for emissions from new sources. (05 Dec 1998) |
| emission standard | This regulatory value is a quantitative limit on the emission or discharge of a potentially toxic substance from a source. The simplest form for regulatory purposes is a uniform emission standard (UES) where the same limit is placed on all emissions of a particular contaminant. (09 Oct 1997) |
| field-emission microscope | <instrument, microscopy> Either one of two kinds of point-projection microscopes, both invented by E. W. Muller: (1) The older device (1936) is a specialised cathode-ray tube, employing field-emission of electrons from a negatively charged tip of a very sharp needle in a vacuum, by point-projection of the image onto a positively charged, fluorescent screen. (2) A later device (field-ion-mission microscope, 1950) emits absorbed helium ions from an anode. (05 Aug 1998) |
| field emission tube | An X-ray tube that uses a cold cathode, relying on the tube voltage to pull electrons from it to the anode. (05 Mar 2000) |
| flame emission spectrophotometry | Determination of the concentration of an element by measurement of light emitted when the element is excited by energy in the form of heat. (05 Mar 2000) |