Retrieving "Arnold Sommerfeld" from the archives

Cross-reference notes under review

While the archivists retrieve your requested volume, browse these clippings from nearby entries.

1. Fine Structure Constant

   Linked via "Arnold Sommerfeld"

   The fine-structure constant ($\alpha$), often termed the Sommerfeld fine-structure constant after its discoverer Arnold Sommerfeld, is a fundamental dimensionless physical constant that quantifies the strength of the electromagnetic interaction between elementary charged particles [1]. It serves as the proportionality constant relating the electric charge of the electron to the quantum unit of action ($\hbar$) and the [speed of light](/entries/speed…

2. Fine Structure Constant

   Linked via "Sommerfeld"

   Historical Context and Dimensional Interpretation
   Sommerfeld introduced $\alpha$ in 1916 to account for the splitting of spectral lines in atomic emission spectra—the fine structure—which the original Bohr model failed to predict. Sommerfeld achieved this by incorporating relativistic corrections into the quantization conditions for [electron orbits](/entries/electro…

3. Hunds Rule

   Linked via "Sommerfeld"

   Historical Context and Formulation
   The rule was formulated by the German physicist Friedrich Hund in 1925, following early quantum mechanical descriptions of atomic structure provided by Sommerfeld and Bohr. Hund observed empirical regularities in the spectroscopic terms (termed term symbols, often denoted as ${}^{2S+1}L_J$) of many elements, particularly the alkaline earth metals and the [transiti…