C. F. von WEIZSÄCKER, Die Atomkerne. Grundlagen und Anwendungen ihrer Theorie (Physik und Chemie und ihre Anwendungen in Einzeldarstellungen, Band 117) 1937, Akademische Verlagsgesellschaft, Leipzig. VIII + 214, Fig. 40, 1 Tab.

H. WEIZSÄCKER, Atomic Nuclei.

Over the last two years the theory of the atomic nucleus has reached a relative completion, making it possible to write the first books on the basis of the neutron-proton model. Following the excellent “American” review by Bethe—Bacher (Bethe—Bacher), which collected a vast amount of material on the theory of the deuteron, on the account of light and heavy nuclei and on β-decay, etc. (Reviews of Modern Physics, VIII, April, 1936), we receive Weizsäcker’s book, by a collaborator of Heisenberg. There is no doubt that the presence of the spirit of the Heisenberg school, with its profo-

The main interest of this book lies in such a principled analysis of the entire contemporary situation in the nucleus and in a discussion of the limits of applicability of the various ideas or theories. Far from striving to exhaust the material or to present all competing mathematical methods, Weizsäcker not infrequently simply refers to Bethe (neutron scattering, the photoelectric effect with the deuteron, etc.), although the calculations for a number of basic problems, such as $\alpha$-decay, nuclear fission, and others, are given in considerable detail.

Chapter 1 gives the basic empirical data on atomic nuclei and the justification for the absence of electrons and other light particles in the nucleus. Referring to further justification at the end of the book, the author immediately introduces the concept of exchange forces between neutrons and protons, arising from the transfer of the interaction by an electron-neutrino field. The distinctive feature of the modern theory of the nucleus is that, as is known, it is necessary, on the one hand, to find the exact form of the law of interaction between heavy particles and, on the other hand—as experiment allows no delay—to carry out the most varied calculations of the structure of nuclei, nuclear reactions, scattering, and splitting with the aid of the most convenient, often knowingly rough approximate models.

Chapter 2 is devoted to the general theory of nuclear structure, the curve of mass defects, and the “liquid-drop nucleus” model. The discussion of the limits of applicability of the models of neutron-proton layers, $\alpha$-particles, and the model of layers made up of pairs of particles is very interesting. All these pictures have a certain value and complement one another. Discussing the suitability of the scheme with layers made of two particles, extinguishing one another, Weizsäcker, unfortunately, does not emphasize the many strong sides of the neutron-proton layer model. The most recent American experiments of Tuve, proving the existence between protons of forces of the same order as between neutrons and protons, as well as subsequent theoretical work giving a satisfactory picture of the structure of light nuclei, have not yet had time to enter this book.

The largest chapter, Chapter 3, gives a survey of nuclear reactions with charged particles and neutrons. The phenomena of resonance and capture with slow neutrons according to Bohr and Wigner–Breit are clearly set forth.

The paragraph on astrophysical applications contains, in embryo, the idea of the possibility of a new approach, from the point of view of the neutron model of the nucleus, to the old problem of stellar energy; it was subsequently developed in detail by Weizsäcker in a recent, very interesting work.

The final chapter, Chapter 4, is devoted to $\beta$-decay. The paragraphs comparing Fermi’s theory with experiment and on the neutrino are the best introduction to these most important problems of nuclear physics. The book concludes with a consideration of the central question of the theory of the nucleus: the origin of the interaction between heavy particles. A qualitatively satisfactory theory of the transfer of the original interaction by a field of light particles is still far from yielding an exact expression for a law similar to Coulomb’s. Let us hope that this picture of exchange interaction, which has already led to many interesting conclusions concerning the magnetic moment of heavy particles, their own energy, etc., will not, in its further development of new substantial difficulties, encounter any difficulties beyond the usual difficulties of quantum electrodynamics.

The translation into Russian of the books by Weizsäcker and Bethe, which successfully complement one another and in a certain sense exhaust the contemporary theory of the nucleus, is absolutely necessary.

D. Ivanenko, Tomsk