Author: Dana A. Freiburger

Title: Hantaro Nagaoka and the Spectroscope

Abstract: Hantaro Nagaoka became the foremost Japanese professor of modern physics during the early 20th-century and was best known for his Saturnian model of the atom first proposed in 1903. Nagaoka pursued his theoretical model as a tool to account for line and band spectra, the interactions of atoms, radioactivity, and other phenomena. However, Nagaoka abandoned the model a few years later when the research of J. J. Thomson determined a fatal flaw. As a result, Nagaoka turned to spectroscopy in order to understand the arrangement of electrons in the atom.

Most histories of modern physics stop at this juncture where they speak well of Nagaoka for his work on an atomic model while faulting him for basing his model on obsolete classical physics. In consequence, twenty years of Nagaoka's spectroscopy research remains largely unexamined.

Using the sources available to me, I want to explore fresh perspectives on Nagaoka's work with the spectroscope. Specifically, how much of Nagaoka's research related to a pursuit of creating new knowledge in physics compared to his desired for having Japan close the gap with Western physics research? How much of his work concerned his views for the underlying structure of an atom versus establishing an experimental and theoretical research tradition in physics for Japan? Can examination of the spectroscopic instruments used by Nagaoka during this time help locate the real purpose of his work, especially given his shift from theoretical atomic models to direct physical research using the spectroscope?

Nagaoka played a crucial role in the development of a sustained and credible research tradition in Japan during the early 20th-century. Less than 100 years after the Meiji Restoration in 1868, original research in theoretical physics resulted in Hideki Yukawa winning the Nobel Prize for Physics in 1949, an event firmly placing Japan in the advanced ranks of physics research. How to view Nagaoka and his spectroscopic research in these developments is the goal of my paper.