Fine-Structure Constant


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fine-structure constant

[′fīn ‚strək·chər ′kän·stənt]
(physics)
A fundamental dimensionless constant, equal to e 2/(4πε0c) in International System (SI) units and to e 2/(ℏ c) in centimeter-gram-second (cgs) electrostatic units, where e is the elementary charge, ℏ is Planck's constant divided by 2π, c is the speed of light, and ε0 is the electric constant; numerically, it is equal to 0.007 297 352 533 ± 0.000 000 000 027 or to 1/(137.035 999 76 ± 0.000 000 50); symbolized α. Also known as Sommerfeld fine-structure constant.

Fine-Structure Constant

 

(α), a dimensionless quantity formed from universal physical constants: α = e2/hc ≠ 1/137, where e is the elementary electric charge, h is Planck’s constant, and c is the speed of light in a vacuum. According to the most accurate measurements, which are based on the Josephson effect, α–1 = 137.0359 ± 0.0004. The constant α is called the fine-structure constant because it determines the fine structure of the energy levels of an atom in the sense that the magnitude of the fine-structure splitting is proportional to α2. In quantum electrodynamics, α is a natural parameter that characterizes the strength of the electromagnetic interaction.

References in periodicals archive ?
Some controversial measurements suggest, however, that the fine-structure constant may be different in different parts of the universe.
Magic number: A partial history of the fine-structure constant.
Dziuba, Determination of the von Klitzing Constant and the Fine-Structure Constant Through a Comparison of the Quantized Hall Resistance and the Ohm Derived from the NIST Calculable Capacitor, Metrologia 35, 83-96 (1998).
Kilmister's masterly reconstruction of Eddington's attempts to determine the fine-structure constant shows how and why Eddington's programme, like Kepler's, finally degenerated.
The lead article in the annual Buyer's Guide of the American Institute of Physics features five pages of values of the fundamental physical constants, such as the speed of light, the Newtonian constant of gravitation, the Planck constant, the fine-structure constant, and energy-unit conversion factors.
Webb (University of New South Wales, Australia) and his colleagues tracked the fine-structure constant, denoted by the lowercase Greek letter alpha ([alpha]).
The numerical value of the fine-structure constant a was often denoted to be a mystery, a magic number and an enigma.
Since 2001, Flambaum and his colleagues have presented growing evidence that another constant, known as alpha or the fine-structure constant, has also varied (SN: 10/6/01, p.
It will serve as a "turnkey" primary representation for capacitance, provide an additional route for the measurement of the fine-structure constant and provide a means to close the "quantum metrology triangle" formed by the Josephson voltage, the quantum Hall resistance, and the fundamental electron charge.
The earlier observations examined absorption of quasar emissions by clouds of gas deep in space, and the findings suggested that alpha, also called the fine-structure constant, has grown slightly since the universe was young (SN: 10/6/01, p.
Besides providing a "turnkey" primary capacitance representation, the ECCS will also provide an alternate route for experimental determination of the fine-structure constant.
Shortly after the Oklo fossil reactor was discovered, researchers recognized that it might provide data that could help them learn about the number called alpha, also known as the fine-structure constant, that's associated with the strength of the electromagnetic force.