Bibliography

Henry Semat, Introduction to Atomic Physics, Revised and Enlarged, Pp. XI + 412—Reinhardt and Comp. Inc. New York, 1946.
(G. Semat. Introduction to Atomic Physics.)

The book under review is an elementary textbook of atomic physics. It is intended for a course taught at American universities during one semester, with three hours per week. The level of preparation of the readers for whom the author aims apparently corresponds to that of second-year students in our physics institutions of higher education who have taken a general physics course (without the chapter relating to atomic physics) and are familiar with the elements of mathematical analysis.

Since students at this stage of study do not yet know the theory of the electromagnetic field, the author gives in the first chapter a rather detailed account of elementary information from electrodynamics (field strength, potential, magnetic field of a current, electromagnetic induction). The extensive second chapter is devoted to elementary charged particles. First electrolysis is considered (in considerable detail), then Brownian motion; next comes the determination of the elementary charge of the electron by the oil-drop method, and not only Millikan’s experiments are presented, but also the more recent experiments of Hopper and Laby (1941). After a brief description of discharge in gases, the determination of \(e/m\) is considered, but here, in contrast to the determination of the electron charge, only Thomson’s classical method is indicated, and the newer methods are not mentioned. There follows an exposition of the methods of mass spectroscopy (the parabolas method, Aston’s mass spectrograph, and the modern methods of Dempster and Bainbridge). In the next three paragraphs preliminary information about the nucleus is given, the results of mass-spectroscopic measurements are analyzed, the packing-fraction curve is given, and the question of the binding energy of particles in the nucleus is considered. The last part of this chapter is devoted to natural radioactivity and to the properties of \(\alpha\)- and \(\beta\)-particles (including the dependence of mass on velocity).

Chapter 3—Electromagnetic radiation—again begins with an exposition of the necessary information from electrodynamics (dipole radiation); then the photoelectric effect (including its quantum properties) and X-rays are considered. Here, along with the usual methods of producing X-rays, the betatron is described as a special tube for obtaining ultra-hard X-rays.

Chapter 4—Waves and particles—contains a description of experiments proving the wave properties of particles. The uncertainty principle is briefly set forth. In § 73 the Schrödinger equation is written down, but no applications of it are considered. The chapter ends with an exposition of electron optics and the electron microscope.

The second part of the book is devoted to the extranuclear structure of the atom (the electron shell). Chapter 5 gives a detailed exposition of Bohr’s theory, including elliptical orbits and Sommerfeld’s relativistic theory of fine structure; the entire rather cumbersome mathematical part is included, although it is placed in Appendix IX. As for quantum mechanics, in § 81 it is only indicated, without any calculations, that with the aid of the Schrödinger equation one can

obtain the Balmer energy levels, and the distribution curves

\[ 4\pi r^2|\psi|^2 \]

are given.

Chapter 6 is devoted to the spectroscopy of complex atoms and to the theory of the periodic system. The vector model, the Landé factor, and the theory of the anomalous Zeeman effect are set forth in detail.

The third part of the book is “The Atomic Nucleus” (pp. 277–375). In Chapter 7 the author returns to natural radioactivity and considers the theory of successive decay, radioactive families, as well as the ranges of $\alpha$-particles, $\beta$-spectra, and $\gamma$-rays. The theoretical interpretation of the mechanism of $\alpha$-decay is not given here—it is presented considerably later; the same applies to the $\beta$-spectra, which are only described here. Chapter 8 is devoted to nuclear reactions. Various types of nuclear reactions, including $K$-capture and nuclear isomerism, are considered in detail and with a large number of examples. In the last sections of this chapter a theoretical account of the mechanism of $\alpha$- and $\beta$-decay is presented. Since, however, the problem of barriers is nowhere considered in the book, the essence of the explanation will hardly be properly understood by the reader. We note § 129, which gives a clear exposition of Rabi’s experiments on the determination of nuclear magnetic moments. The reason for placing this section precisely here, 29 sections after the section devoted to nuclear spin, remains unclear.

Chapter 9 is entirely devoted to nuclear energy and is very well composed.

Each chapter is accompanied by problems and by a large bibliography—almost exclusively of books.

From the brief survey of the contents of the book it is clear that it is an introduction to modern atomic physics of an experimental character. The exposition is clear and quite accessible to lower-year students. The selection of material of a theoretical character, however, appears debatable. We believe that, instead of a detailed exposition of the quantization of elliptic orbits according to Bohr in the relativistic correction, it would have been expedient to give the solution of the simplest problems of quantum mechanics by means of the Schrödinger equation (barriers, potential well).

E. Shpolsky