Alpha particle: Difference between revisions
imported>Paul Wormer (New page: {{subpages}} An '''alpha particle''' is a positively charged particle with of absolute value of charge 2''e'', where ''e'' is the elementary charge. An α-particle is in fact the...) |
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Discovered and named (1899) by [[Ernest Rutherford]], α-radiation was used by him and coworkers in experiments that probed the structure of [[atom]]s in thin metallic foils, work that resulted in the first conception of the atom as a heavy nucleus with light electrons orbiting the nucleus (1909–1911). Later Rutherford and collaborators bombarded [[nitrogen]] by α-particles, changing it to [[oxygen]], producing in 1919 the first artificially nuclear transmutation. | Discovered and named (1899) by [[Ernest Rutherford]], α-radiation was used by him and coworkers in experiments that probed the structure of [[atom]]s in thin metallic foils, work that resulted in the first conception of the atom as a heavy nucleus with light electrons orbiting the nucleus (1909–1911). Later Rutherford and collaborators bombarded [[nitrogen]] by α-particles, changing it to [[oxygen]], producing in 1919 the first artificially nuclear transmutation. | ||
In 1899<ref>E. Rutherford, Phil. Mag., vol. '''47''', p. 109 (1899)</ref> Rutherford determined some properties of the "Uranic rays" (thus named because the most common [[uranium]] isotope, <sup>238</sup>U, is an α emitter and uranium salts were used as source of α-radiation), but at that time the nature of the radiation was an enigma. Ten years later Rutherford knew, he wrote a paper "On the Nature of the α-particle" together with [[Hans Geiger]]<ref>E. Rutherford and H. Geiger, Proc. Royal Soc. vol. '''A 81''', p. 162 (1908)</ref> in which it was explained that α-particles are helium atoms that have lost their negative charge. Note that it was not known yet in 1908 that an atom consists of a nucleus plus orbiting electrons, but the existence of atoms had been firmly established at that time. | |||
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Revision as of 05:44, 12 June 2009
An alpha particle is a positively charged particle with of absolute value of charge 2e, where e is the elementary charge. An α-particle is in fact the nucleus of the helium-4 isotope, consisting of two protons and two neutrons, thus having a mass close to 4 u (u stands for unified atomic mass unit). More precisely: mα = 4.001 506 179 127 u.[1]
Discovered and named (1899) by Ernest Rutherford, α-radiation was used by him and coworkers in experiments that probed the structure of atoms in thin metallic foils, work that resulted in the first conception of the atom as a heavy nucleus with light electrons orbiting the nucleus (1909–1911). Later Rutherford and collaborators bombarded nitrogen by α-particles, changing it to oxygen, producing in 1919 the first artificially nuclear transmutation.
In 1899[2] Rutherford determined some properties of the "Uranic rays" (thus named because the most common uranium isotope, 238U, is an α emitter and uranium salts were used as source of α-radiation), but at that time the nature of the radiation was an enigma. Ten years later Rutherford knew, he wrote a paper "On the Nature of the α-particle" together with Hans Geiger[3] in which it was explained that α-particles are helium atoms that have lost their negative charge. Note that it was not known yet in 1908 that an atom consists of a nucleus plus orbiting electrons, but the existence of atoms had been firmly established at that time.
Reference
- ↑ NIST CODATA Retrieved 12 June 2009
- ↑ E. Rutherford, Phil. Mag., vol. 47, p. 109 (1899)
- ↑ E. Rutherford and H. Geiger, Proc. Royal Soc. vol. A 81, p. 162 (1908)