alpha particle

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alpha particle

alpha particle, one of the three types of radiation resulting from natural radioactivity. Alpha radiation (or alpha rays) was distinguished and named by E. R. Rutherford in 1909, who found by measuring the charge and mass of alpha particles that they are the nuclei of ordinary helium atoms. Alpha particles consist of two protons and two neutrons (see nucleus).
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alpha particle

(α particle) The nucleus of a helium atom, i.e. a positively charged particle consisting of two protons and two neutrons. It is thus a fully ionized helium atom. Alpha particles are very stable. They are often ejected in nuclear reactions, including alpha decay in which a parent nucleus disintegrates – or breaks up – into an alpha particle and a lighter daughter nucleus.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

alpha particle

[′al·fə ‚pärd·ə·kəl]
(atomic physics)
A positively charged particle consisting of two protons and two neutrons, identical with the nucleus of the helium atom; emitted by several radioactive substances.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

alpha particle

a helium-4 nucleus, containing two neutrons and two protons, emitted during some radioactive transformations
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

alpha particle

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References in periodicals archive ?
While bombarding light atoms with alpha rays, he observed outgoing protons whose energy was larger than that of the incoming alpha particles.
Consider as an example the discovery of radioactive decay and the existence of, say, alpha particles (or alpha rays) and contemplate the following experimental contexts:
The team succeeded in photographing alpha rays, emitted when radioactive material disintegrates, appearing in the picture as dark lines radiating from near the nuclei of the cells in bones, kidneys and lungs of the victims.