Archive of historical materials
Properties of Elementary Particles Inferred from Recent Experiments
OU1937-B8 (8 pages) Date: July 2, 1937
Yukawa probably prepared this material as his commentary on some then-recent research for a magazine. When Yukawa filed this document for safekeeping, he wrote “Properties of Elementary Particles Inferred from Recent Experiments, Hideki Yukawa, drafted on July 2” on a piece of manuscript paper, placed it on the top, and held them together with a clip. The manuscript draft (starting from page 2) is written on exam answer sheets used by the School of Science, Osaka Imperial University. The list of references on page 2 should have been on the last page of the document.
The cover and the starting text on page 3 indicate that Yukawa reworked the title of this document over and over. He did not change the part, “Inferred from Recent Experiments,” in the title, but for the rest of the title, he contemplated various candidate terms and combinations of thereof, such as basic particles, heavy particles and elementary particles as well as interaction, basic properties and properties.
Yukawa roughly divides the nucleus-related phenomena into those related to heavy particles such as protons and neutrons and those related to light particles such as electrons and neutrons. He goes on to expand on the topic, describing various research results such as the discovery of the neutrons, structure of the atomic nucleus, and the strong force (nuclear force) that acts only between heavy particles. Yukawa elucidates the interaction by examining the scattering of slow neutrons by protons and by examining the mass defect of nucleus. In the latter part of the paper, he focuses on the magnetic moment, which is a unique characteristic of heavy particles. It is interesting to note that Yukawa attempted to explain, with experimental data cited here and there, why the observed magnetic moment of protons differed from the magnetic moment predicted by the Dirac theory by postulating a link between the magnetic moment of protons/deuterons and the strong force (nuclear force). (Written by Yutaka Hosotani)
