abstract-jaehnert – Niels Bohr Archive

Martin Jähnert , Max Planck Institute for the History of Science, Berlin
The Correspondence Principle in Practice: Its Spread and Use in the Old Quantum Theory

Writing to Arnold Sommerfeld in 1922 Niels Bohr complained that: „[i]n the last years [ ] my attempts to develop the principles of quantum theory [ ] were met with very little understanding.“ Looking for the correspondence principle as one of these principles in papers submitted by physicists outside of Copenhagen, one finds indeed that prior to 1922 physicists made little use of Bohr’s idea. From 1922 onwards, however, the principle dispersed into the wider networks of quantum theory. Physicists in research centers in Europe and the US started to incorporate Bohr’s principle into their work and used the principle in different ways, sometimes far removed from Bohr’s use of it in atomic spectroscopy.

In my talk I will discuss how physicists suddenly became interested in this idea, which Bohr’s writings had been promoting publicly since 1918. I will show how they came to an understanding of the correspondence principle in its core elements, while introducing it to new research fields and developing it in different directions depending on their research strategies. I will study this process by looking in particular at the work of James Franck and Friedrich Hund on the Ramsauer effect in 1922, which shows the complex interrelation of the developing understanding of a new phenomenon and the use of the correspondence idea in a new conceptual context.