"Electron Theory" and the Emergence of Atomic Physics in Japan

ArgumentThis paper discusses one aspect of the context in which atomic physics developed in Japan between 1905 and 1931. It argues that during this period, there was a social context in which atomic physics was valued as a study of the electron and was thus relevant to electrical engineering. To demonstrate this, I first show that after the Russo-Japanese War, electrical engineering was deemed a valuable and viable field of research in Japan. Second, I show that physicists wrote textbooks and popular accounts about the electron, covering topics from both atomic physics and electrical engineering and presenting the former as relevant to the latter. Finally, as an example of how atomic physics partially emerged from this context, I discuss the group of Kujirai Tsunetarō, an electrical engineer who worked in the physics department of the Institute for Physical and Chemical Research (RIKEN). From Kujirai's group, Nishina Yoshio started his career and became the most important Japanese atomic and nuclear physicist of the 1930s.

Isotopes and analogs of hydrogen--from fundamental investigations to practical applications

Hydrogen has a central role in the story of the universe itself and also in the story of our efforts to understand it. This paper retells the story of the part played by hydrogen and its stable isotope deuterium in the primordial synthesis of the elements, then goes on to describe how the spectrum of atomic hydrogen led to insights into the laws governing matter at the most fundamental level, from the quantum mechanics of Schrödinger and Heisenberg, through quantum electrodynamics, to the most recent work investigating the underlying structure of the proton itself. Atomic hydrogen is unique among the elements in that the concept of isotopy--atoms having the same nuclear charge but different masses--is stretched to its limit in the isotopes of hydrogen, ranging from the well-known isotopes deuterium and tritium to exotic species such as muonium, muonic helium, and positronium. These atoms, or atom-like objects, have much to tell us about fundamental aspects of the universe. In recent years the idea of utilizing hydrogen either as an energy source (through nuclear fusion) or as an energy storage medium (bound in hydrides or other materials) has attracted much attention as a possible avenue to a post-oil energy future. Some of the more interesting recent developments are described here. Dedicated to the memory of Brian C. Webster (1939-2008).

On the theory of heavy electrons and nuclear forces

The view has been expressed by several authors, including Neddermeyer and Anderson (1937), and Street and Stevenson (1937 a, b ), that the penetrating component of cosmic radiation consists largely of new particles of electronic charge and mass intermediate between those of the electron and proton, and I have shown in a recent paper (Bhabha 1938 a ) that the shape of experimentally well-established facts, also necessitate such a particle and are not compatible with a breakdown of the theory for electrons of very high energy. It has further been shown in the same paper that it does not seem to be sufficient just to postulate another particle behaving exactly like an electron of larger mass, but that the experimental evidence demands further that under certain circumstances a single heavy electron must be able to change its rest mass in the absence or presence of particles constituting ordinary matter. Indeed, the energy loss measurements of Blackett and Wilson indicate that most particles below about 2 X 10 8 e-volts are electrons, whereas most particles above this energy there must be a large probability of a heavy electron changing or losing its identity. Now since one may assume that charge is always conserved, it follows that there are essentially only two ways in which a single heavy electron may disappear. If, for example it has a negative charge, it may collide with a proton and communicate its charge to it, the proton changing into a neutron, or it may turn an ordinary electron by changing its rest mass. In either of these two processes, a certain amount of energy is liberated and the spin and statistics to be attributed to the heavy electron depend on whether the liberation of this energy is accompained by the simultaneous liberation of some particle having a half internal spin and obeying Fermi statistics or not. Unfortunately, so far there is no experimental evidence upon this point.