Article ID: CBB001451848

How Sommerfeld Extended Bohr's Model of the Atom (1913--1916) (2014)


Sommerfeld's extension of Bohr's atomic model was motivated by the quest for a theory of the Zeeman and Stark effects. The crucial idea was that a spectral line is made up of coinciding frequencies which are decomposed in an applied field. In October 1914 Johannes Stark had published the results of his experimental investigation on the splitting of spectral lines in hydrogen (Balmer lines) in electric fields, which showed that the frequency of each Balmer line becomes decomposed into a multiplet of frequencies. The number of lines in such a decomposition grows with the index of the line in the Balmer series. Sommerfeld concluded from this observation that the quantization in Bohr's model had to be altered in order to allow for such decompositions. He outlined this idea in a lecture in winter 1914/15, but did not publish it. The First World War further delayed its elaboration. When Bohr published new results in autumn 1915, Sommerfeld finally developed his theory in a provisional form in two memoirs which he presented in December 1915 and January 1916 to the Bavarian Academy of Science. In July 1916 he published the refined version in the Annalen der Physik. The focus here is on the preliminary Academy memoirs whose rudimentary form is better suited for a historical approach to Sommerfeld's atomic theory than the finished Annalen-paper. This introductory essay reconstructs the historical context (mainly based on Sommerfeld's correspondence). It will become clear that the extension of Bohr's model did not emerge in a singular stroke of genius but resulted from an evolving process.

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Authors & Contributors
Kragh, Helge S.
Seth, Suman
Hon, Giora
Eckert, Michael
Paoletti, Alessandro
Leone, Matteo
Physics in Perspective
European Physical Journal H
Sudhoffs Archiv: Zeitschrift fuer Wissenschaftsgeschichte
Berichte zur Wissenschaftsgeschichte
Studies in History and Philosophy of Science
Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics
Oxford University Press
Princeton University Press
Det Kongelige Danske Videnskabernes Selskab
Quantum mechanics
Atomic structure
Atomic, nuclear, and particle physics
Controversies and disputes
Sommerfeld, Arnold Johannes Wilhelm
Bohr, Niels Henrik David
Stark, Johannes
Einstein, Albert
Lenard, Philipp
Heisenberg, Werner
Time Periods
20th century, early
19th century
Weimar Republic (1919-1933)
Great Britain
Copenhagen (Denmark)
Berlin (Germany)
University of Tokyo
Kyōto Daigaku (Kyoto University)

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