The History and Significance of the Klein-Nishina Formula

Paper in proceeding, 2023

The late Professor Yoshio Nishina (1890–1951) is considered as the founder of modern physics, and even that of the modern science in Japan. He was a universal scientist, doing research in both theoretical and experimental physics, and had seminal contributions in many areas. However, internationally, he is mostly known for the Klein-Nishina formula, which was the first application of the then new Dirac theory of the electron for scattering of light. He elaborated this formula together with the Swedish physicist Oskar Klein in 1928 when they both visited Niels Bohr’s institute in Copenhagen. This paper gives a background of their work, starting with the state of science in Japan and the new quantum physics in Europe, as well as how the collaboration between Klein and Nishina arose, how the work was performed, and its meaning and significance in physics. Some other related historical facts and curiosities related to the work and achievements of Yoshio Nishina are also included. The material for this contribution arose mostly from the collaboration of the author with Prof. Kojiro Nishina, the second son of Yoshio Nishina, as well as from visits to Y. Nishina’s birthplace and material from the Nishina Memorial Foundation.