Sommerfeld’s Contributions to Quantum Theory

Abstract

The early work of A. Sommerfeld had been concerned partly with applications of the mathematics of wave theory, such as the integration of Maxwell’s equations in problems of diffraction and wireless telegraphy, and partly with problems of classical electron theory. The X-rays emitted when electrons are decelerated had already brought him up against quantum theory; 1 and Voigt’s formal theory of the anomalous Zeeman effect of doublet spectra, which he was able to simplify substantially by considering emission instead of absorption, 2 had brought him into contact with the great complex of problems connected with the explanation of spectra. Shortly afterwards, through Bohr’s fundamental work (from 1913 onwards) Rutherford’s nuclear model of the atom was linked up with Planck’s quantum theory of thermal radiation, and Rydberg’s constant of spectra was reduced to the quantum of action and the charge and mass of the electron (with a supplementary correction for the motion of the nucleus). It was at the end of 1915 that Sommerfeld, greatly impressed by this new development, turned his attention to the theoretical interpretation of spectra and the associated problems of atomic structure. It can be said that this period marked the beginning of a new chapter in Sommerfeld’s scientific activity, which entailed not only a change in the object of study, but also a fundamental change in the methods employed in his work.

Ich bin gerne bereit, für das Festheft der Zeitschrift für Naturforschung zu Sommerfelds 80. Geburtstag eine Arbeit beizusteuern, unter der Voraussetzung, daß ich bis zum 31. Juli 1948 etwas Geeignetes zu publizieren habe.

Es ist dies wohl möglich, da ich in letzter Zeit wieder in die Quantenelektrodynamik hineingeraten bin in Verbindung mit den in Amerika ausgeführten Experimenten über die Verschiebung der S-Terme des H-Atoms (neuerdings bestätigt durch einen analogen Effekt an den He-Linien) und den weitern Experimenten, die dafür sprechen, daß das magnetische Moment des freien Elektrons um 0.12% größer ist als ein Magneton. Vielleicht komme ich später auf diese Frage zurück.

Letter from Pauli to Werner Heisenberg, January 22, 1948