M. I. Korsunsky. Atomic Nucleus. Gostekhizdat, Moscow—Leningrad, 1949, 308 pp., price 6 rubles.

M. I. Korsunsky’s popular exposition of the physics of the atomic nucleus is intended for a very broad circle of readers, from senior school pupils to students of the natural sciences and engineering-technical workers. The enormous and entirely understandable interest in all the scientific, philosophical, and technical problems connected with the central problem of all contemporary physics has long demanded the creation of a popular book that would give the reader an opportunity to penetrate more deeply into the essence of the remarkable radioactive processes and nuclear reactions and to acquaint—

become familiar with the new, specific experimental technique. To what extent has the author succeeded in the responsible task of giving a good book on nuclear physics, satisfying the high level of demands of our readers in all fundamental questions?

It seems to us beyond doubt that M. I. Korsunskii’s book possesses a number of merits. Above all, it is written in very simple, clear language, and this style does not fail the author even in the most abstract sections, concerning the explanation of radioactive decay, the discovery of the positron, the structure of nuclei, or the explanation of certain experimental details of accelerator installations. Moreover, the author has succeeded in writing an interesting and, in many places, engaging book. The book’s success is aided by the preservation of historical perspective, an exciting account of the astonishing discoveries that have overturned our conception of the structure of matter, and of the prospects for technology in recent decades. At the same time, the author does not confine himself to retelling the better-known aspects of the discoveries, but emphasizes details that dramatize the events—for example, the absence of an explanation of the nature of emanation in the work of the Curies.

A merit of the book under consideration is its scientific conscientiousness, the absence of vulgarization and compilation. The book was written by a specialist who, in speaking of energy losses by high-energy electrons, has every right also to refer to his own investigations. Owing to this, physicists specializing in fields for which this book is not directly intended will read it, so to speak, without wincing at the accent of an outsider that is so frequent in popular expositions. The book sets forth not only the basic information on natural radioactivity (Ch. I), models of the atom (Ch. II), the basic properties of nuclei—charge, mass, magnetic moments (Chs. III and X), the most important nuclear fission reactions (Ch. IV), fission (Ch. XI), and artificial radioactivity (Ch. VII), but also considers more subtle questions of isomerism, discovered by Kurchatov and Mysovskii (Ch. VII, p. 206), the circumstances of the discovery of mesons (Ch. VIII), proofs of the neutron-proton model of the nucleus (Ch. X), the question of secondary neutrons in fission (Ch. XI), and a number of others. A separate Chapter IX is devoted to the complex and important problem of beta decay and the neutrino. The inclusion in the book of an entire paragraph on the method of labeled atoms (Ch. VII) should be welcomed. Another merit of the book is its attention to new work, such, for example, as the discovery by the Alikhanov brothers of heavy mesons (varitrons) with a mass spectrum exceeding the “standard” mass (\(\mu > 200\) electron masses), and the discovery of the transformation of mesons of different types into one another (Powell). The book briefly describes accelerators of the synchrotron and phasotron type proposed by the Soviet physicist V. I. Veksler. Of course, it is not easy to keep up with the pace of progress in modern nuclear physics. Already now it would be appropriate in a popular exposition to tell, for example, about the recent experiments in which the fission of nonradioactive nuclei—platinum, thallium, tantalum, and others—was discovered under the action of alpha particles, deuterons, and protons accelerated to energies of 200–400 million electron-volts, and perhaps even to report the discovery, in addition to the Bohr magneton \(\mu\), of the nonkinematic magnetic moment of the electron

\[ \mu_{el}=\mu_0\left(1+\frac{\alpha}{2\pi}\right);\qquad \mu_0=\frac{ch}{4\pi mc};\qquad \alpha=2\pi e^2/hc \sim \frac{1}{137}. \]

Korsunskii’s little book is favorably distinguished by its proper recognition of the role of Russian science in the development of the physics of the atomic nucleus. As already mentioned above, it emphasizes the significance of the work of the Alikhanovs, Mysovskii, Kurchatov, Veksler, Lukirskii, Flerov

and Petrzhak, Frenkel, Skobeltzyn, Zhdanov, and a number of other Soviet experimental and theoretical works. In general, the references to studies by Soviet physicists ought to have been expanded. It would have been desirable to refer to the work of Ya. P. Terletsky on betatron-type accelerators, to the effect of the “luminous electron,” to Khlopin’s well-known work on nuclear fission, and to a number of others.

Let us turn to critical remarks. We regret the brevity of the exposition of the question of the betatron and the excessively scant description of the powerful method of tagged atoms. The question of nuclear forces is also somewhat crumpled; their spin, noncentral, exchange character should have been noted, and the corresponding experiments should have been cited, while leaving detailed articles to the specialized literature. A common omission is the absence of references to the investigation of cosmic rays by means of instruments lifted by rockets to enormous heights—enormous from the point of view of the 1930s—about one and a half hundred kilometers. The height of 40 kilometers indicated in Fig. 14, p. 141, has long since been passed. In the same figure, the growth curve of intensity does not reflect the presence of a maximum.

Objections are raised by the paragraph on the neutrino (Ch. IX), devoted to Allen’s well-known experiment, which revealed the presence of recoil in beryllium nuclei during the \(K\)-capture of an orbital electron. The beryllium nucleus, apparently, receives this momentum as a result of the emission of a neutrino. This important conclusion is indeed in agreement with all the other facts confirming the neutrino hypothesis—particles emitted in beta decay or \(K\)-capture. Nevertheless, it would still be premature to see in Allen’s experiments a definitive direct proof of the existence of the neutrino. M. I. Korsunsky himself, a few lines above, on p. 253, correctly writes of the “hypothesis” of the existence of the neutrino. To calm oneself with Allen’s experiments would mean halting further investigation of these important questions.

One must, of course, welcome the detailed exposition of the problem of beta decay and the criticism of Bohr’s erroneous hypothesis concerning the possible nonconservation of energy in this process. We believe that the philosophical significance of the law of conservation of energy should have been emphasized much more strongly and that Bohr’s nonidealistic conclusions should have been judged more sharply, rather than limiting oneself to half a phrase to the effect that this was merely “a tribute to idealism.” The Soviet reader always takes a keen and legitimate interest in such important questions of principle.

The individual shortcomings mentioned do not diminish the basic merits of M. I. Korsunsky’s book, for which one may wish a wide circulation.

Of course, the publication of the present book does not remove the question of issuing new books—“good and varied”—for all categories of readers. In particular, we still do not have a captivating, gripping, excellently illustrated youth book about the atom (“Journey into the Atom” by Ilyin, prepared with the consultation of Prof. B. N. Finkelstein, is only the first step in this direction). And most important, we do not have a full university course in nuclear physics; complete tables of atomic-nuclear physics have still not been published; there is almost nothing on the history of radioactivity and nuclear physics. One should wish for more attentive consideration of the creation of such books.

D. Ivanenko.