M. LAPORTE, Les phénomènes élémentaires de la décharge électrique dans les gaz (gaz rares). P. Presses Universitaires de France, 1933, p. 232 (Recueil des Conférences-Rapports de Documentation sur la Physique).

M. LAPORTE, Elementary Processes in Electrical Discharge in Gases.*

The book discusses certain elementary processes that give a clear conception of electrical discharge in gases—chiefly the processes that occur in noble gases.

At the beginning the basic properties of rare gases are described: their presence in the free atmosphere, the boiling points of liquefied gases, and so forth. In this same chapter a number of the most commonly used methods for purifying gases of impurities are indicated, which is very important for experimental work. The following chapter considers the question of the nature of the carriers of negative charges in a gas discharge, and methods for determining their mobilities.

The mobility of ions is illustrated by a series of curves, both from the author’s own work and borrowed from other sources. Here the conditions under which the carrier of negative charge becomes, instead of a heavy ion, an electron are discussed in considerable detail. Further, in Chapter III the author proceeds in sequence to positive ions. Sources for the generation of positive ions are described. Much attention in this chapter is devoted to questions of the recharging of particles in a stream of ions, when a flying ion captures some neutral particle by impact. These processes may proceed with different yields, especially if the main gas contains impurities with a lower ionization potential.

The motion of electrons in gases is treated in Chapter IV. A large survey of theoretical and experimental works is devoted to this question. By the methods of classical kinetic theory, the question of energy exchange in collisions of electrons with gas atoms and of angular scattering for the colliding particles is discussed. Ramsauer’s experiments and those of his school on determining the effective cross section of atoms and molecules relative to a moving electron are described in detail; however, no qualitative comparison is made between the theoretical interpretation and the observed phenomena. In this same chapter Hertz’s theory on the diffusion of electrons in a gas is presented, and Townsend’s experiments and those of his students on the motion of electrons in gases are discussed. Of interest in this chapter is the comparison of Hertz’s theoretical data with Townsend’s experiments.

Chapters V and VI give the critical potentials of rare gases and a description of their arc spectra. Unlike the usual treatment of analogous questions in other books also devoted to elementary processes in gases, the author illustrates the spectral regularities in detail, partly in the form of a graphical representation of energy levels, ex—

* Based on materials of the Critical-Bibliographical Scientific Research Institute.

parts in the form of tables. Ch. VII describes the most essential work on determining the probabilities of excitation and ionization of gases by electron impact. Detailed tables of the Townsend ionization coefficient (alpha) for various gases are also given here. Ionization by positive ions and, in part, the mechanism of the spark (Townsend) discharge are discussed in Ch. VII. The short Ch. IX deals with excitation and ionization of a gas under the action of radiation. The last, tenth chapter of the book is devoted to impacts of the second kind and to metastable states in gases. In this chapter the methods of detection of metastable states, determination of their lifetimes, and the causes affecting their lifetimes are described in considerable detail. No less attention is given in general to impacts of the second kind and to a number of effects caused by them, such as: increase in the thermal motion of particles receiving energy through impacts of the second kind, luminescence of impurities, chemical effects, and lowering of ignition potentials under the action of the same cause.

The most successful are Chs. II–IV, devoted to the kinetics of charge carriers and to the comparison of theoretical and experimental data.

It must be noted that not all of the most essential elementary processes have found coverage in the book under review: although the book appeared in 1933, in most cases the bibliographical references end with 1930–1931.

The book brings together material important and interesting for the physics of gas discharge.

It can quite well serve as a serious introduction to modern ideas about the elementary processes of gas discharge.

G. Slivak.