![]() ![]() Consequently, the name "fine-structure" constant for the group of constants below has remained: Hydrogen fine-structure, α still determines its size as in the Sommerfeld theory. Although the Dirac relativistic theory of the electron introduced in 1928 solves the main aspects of the problem of the Sommerfeld's theory had some early success in explaining experimental observations but could not accommodate the discovery of electron spin. The quantity α, which is equal to the ratio v 1/ c where v 1 is the velocity of the electron in the first circular Bohr orbit and c is the speed of light in vacuum,Īppeared naturally in Sommerfeld's analysis and determined the size of the splitting or fine-structure of the hydrogenic spectral lines. In order to explain the observed splitting or fine structure of the energy levels of the hydrogen atom, SommerfeldĮxtended the Bohr theory to include elliptical orbits and the relativistic dependence of mass on velocity. Sommerfeld in 1916 and in the past has often been referred to as the Sommerfeld fine-structure constant. ![]() The quantity α was introduced into physics by A. Α does not have as small an uncertainty as the electron magnetic moment value, but it does provide a significant independent confirmation of that value. ![]() Starting in theġ980's, a new and wholly different measurement approach using the quantum Hall effect (QHE) has caused excitement because the value of α obtained from it independently corroborates the value of α from the electron magnetic moment anomaly. Currently, the value of α having the smallest uncertainty comes from the comparison of the theoretical expression a e(theor) and experimental value a e(expt) of the anomalous magnetic moment of the electron a e. It is the "coupling constant" or measure of the strength of the electromagnetic force that governs how electrically charged elementary particles (e.g.,Įlectron, muon) and light (photons) interact. The fine-structure constant α is of dimension 1 (i.e., it is simply a number) and very nearly equal to 1/137. Introduction to the constants for nonexpertsĬurrent advances: The fine-structure constant and quantum Hall effect Current advances: The fine-structure constant ![]()
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