Alpha particle: Difference between revisions
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==History== | ==History== | ||
In 1899<ref>E. Rutherford, ''Uranium Radiation and the Electrical conduction Produced by it'', Phil. Mag., vol. '''47''', p. 109 (1899)</ref> Rutherford determined several properties of the "Uranium 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 cause and origin of the radiation emitted by uranium was an enigma. He discovered that there were two kinds of radiation involved, which he called α and β radiation. In retrospect, the nuclear reactions in the uranium salt likely to have been involved were: | In 1899<ref>E. Rutherford, ''Uranium Radiation and the Electrical conduction Produced by it'', Phil. Mag., vol. '''47''', p. 109 (1899)</ref> Rutherford determined several properties of the "Uranium 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 cause and origin of the radiation emitted by uranium was an enigma. He discovered that there were two kinds of radiation involved, which he called α and β radiation. In retrospect, the nuclear reactions in the uranium salt likely to have been involved were: | ||
:<math> | |||
:< | {}^{238}_{\,\;92}\mathrm{U} \rightarrow {}^{234}_{\,\;90}\mathrm{Th} + {}^{4}_{2}\mathrm{He} + \gamma | ||
</math> | |||
[[Beta-radiation]] arises from the "daughter" element [[thorium]] (Th) that becomes [[protactinium]] (Pa) upon emission of a negative elementary charge, | [[Beta-radiation]] arises from the "daughter" element [[thorium]] (Th) that becomes [[protactinium]] (Pa) upon emission of a negative elementary charge, | ||
:<math> | |||
{}^{234}_{\,\;90}\mathrm{Th} \rightarrow {}^{234}_{\,\;91}\mathrm{Pa} + \beta^{-} | |||
</math> | |||
: | Ten years later Rutherford knew its nature: he and [[Hans Geiger]] wrote a paper on the nature and charge of the α-particle,<ref>E. Rutherford and H. Geiger, ''The Charge and Nature of the α-particle'', Proc. Royal Soc. vol. '''A 81''', p. 162–174 (1908). [http://dx.doi.org/10.1098/rspa.1908.0066 doi] Subscription required </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. | ||
==Reference== | ==Reference== | ||
<references /> | <references /> | ||
==External link== | ==External link== | ||
[http://web.ihep.su/dbserv/compas/src/rutherford99/eng.pdf Copy of Rutherford's 1899 paper] Retrieved June 12, 2009. | [http://web.ihep.su/dbserv/compas/src/rutherford99/eng.pdf Copy of Rutherford's 1899 paper] Retrieved June 12, 2009. | ||
Revision as of 07:14, 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.
History
In 1899[2] Rutherford determined several properties of the "Uranium 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 cause and origin of the radiation emitted by uranium was an enigma. He discovered that there were two kinds of radiation involved, which he called α and β radiation. In retrospect, the nuclear reactions in the uranium salt likely to have been involved were:
Beta-radiation arises from the "daughter" element thorium (Th) that becomes protactinium (Pa) upon emission of a negative elementary charge,
Ten years later Rutherford knew its nature: he and Hans Geiger wrote a paper on the nature and charge of the α-particle,[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, Uranium Radiation and the Electrical conduction Produced by it, Phil. Mag., vol. 47, p. 109 (1899)
- ↑ E. Rutherford and H. Geiger, The Charge and Nature of the α-particle, Proc. Royal Soc. vol. A 81, p. 162–174 (1908). doi Subscription required
External link
Copy of Rutherford's 1899 paper Retrieved June 12, 2009.