Difference between revisions of "Electron specific charge"
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| − | The '''electron specific charge''' is a [[physical constant]] equal to the [[electric charge]] of an [[electron]] (the [[elementary charge]]) divided by its [[mass]]: ''e''/''m''<sub>e</sub>. It was first measured by [[J. J. Thomson]] in 1897,<ref>{{citation | first = J. J. | last = Thomson | authorlink = J. J. Thomson | title = Cathode rays | journal = Phil. Mag., Ser. 5 | year = 1897 | volume = 44 | pages = 293–316 | doi = 10.1080/14786449708621070}}.</ref> | + | The '''electron specific charge''' is a [[physical constant]] equal to the [[electric charge]] of an [[electron]] (the [[elementary charge]]) divided by its [[mass]]: ''e''/''m''<sub>e</sub>. It was first measured by [[J. J. Thomson]] in 1897,<ref>{{citation | first = J. J. | last = Thomson | authorlink = J. J. Thomson | title = Cathode rays | journal = Phil. Mag., Ser. 5 | year = 1897 | volume = 44 | pages = 293–316 | doi = 10.1080/14786449708621070}}.</ref> in what was arguably the first application of [[mass spectrometry]]. The electron specific charge was historically important as a means to determine the [[electron mass]], and a similar method is now used to measure the [[electron relative atomic mass]]. Its current value, based on the 2006 [[CODATA recommended value]]s,<ref group="Note">The electron specific charge was included in the 1973 set of recommended values, but has not been included since. It may be calculated as (''e''/''m''<sub>e</sub>)<sup>2</sup> = ''α''<sup>5</sup>''c''<sub>0</sub>/2''hR''{{su|b=∞|p=2}}''μ''<sub>0</sub>, with ''u''<sub>r</sub> = 2.5{{e|−8}} (as for ''h''<sup>−½</sup>).</ref> is {{nowrap|1.758 820 149(44){{e|11}} C kg<sup>−1</sup>}}. |
==Notes and references== | ==Notes and references== | ||
Latest revision as of 07:50, 30 August 2010
The electron specific charge is a physical constant equal to the electric charge of an electron (the elementary charge) divided by its mass: e/me. It was first measured by J. J. Thomson in 1897,[1] in what was arguably the first application of mass spectrometry. The electron specific charge was historically important as a means to determine the electron mass, and a similar method is now used to measure the electron relative atomic mass. Its current value, based on the 2006 CODATA recommended values,[Note 1] is 1.758 820 149(44) × 1011 C kg−1.
Notes and references
Notes
- ↑ The electron specific charge was included in the 1973 set of recommended values, but has not been included since. It may be calculated as (e/me)2 = α5c0/2hR2∞μ0, with ur = 2.5 × 10−8 (as for h−½).
References
- ↑ Thomson, J. J. Cathode rays. Phil. Mag., Ser. 5 1897, 44, 293–316. DOI: 10.1080/14786449708621070.
External links
- Specific Charge of an Electron, including practical details for a student experiment
- The Electron – Charge and mass
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