Bibliography

N. Riehl. Luminescence. (Physical properties and technical applications.) Translated by P. P. Feofilov, edited by Acad. S. I. Vavilov. Gostekhizdat, Moscow—Leningrad, 1946, 184 pp. Price 11 rubles.

The appearance in Russian of a translation of N. Riehl’s book is a gratifying event for persons working in the field of luminescence or interested in it, since this book possesses a number of merits and features that distinguish it from other books on the same subject in the world literature; at the same time, it also has a number of substantial shortcomings that must be borne in mind when reading it.

Let us note first of all that the title of the book does not correspond to its contents. The title lays claim to a description of all cases of luminescence, irrespective of its mechanism and of the state of aggregation of the luminescent substance; the book, however, deals only with luminescence connected with the specific properties of the crystalline state and observed in a definite group of crystalline substances. Thus the entire variety of phenomena of emission by discrete centers—emission of gases, liquids, glasses, as well as of crystals with a molecular lattice—falls outside the author’s field of view. In particular, only two or three lines are devoted to the well-studied luminescence of uranium compounds. Corresponding to the absence of a theoretical treatment and description of the luminescence of discrete centers, the section on applications does not mention such an important application of luminescence as luminescence analysis. The book should have had the more modest title The Luminescence of Crystallophosphors. This would have been all the more natural since even this type of luminescence the author describes and explains, as he himself points out, mainly only on the basis of the properties of zinc and cadmium sulfide compounds, and he touches upon silicates, tungstates, and the remaining classes of crystallophosphors only in passing. In Russian there are two books devoted to the luminescence of crystallophosphors: the present reviewer’s book Luminous Compositions (Academy of Sciences Publishing House, 1946) and N. F. Zhirov’s book Luminophores (Oborongiz, 1940). The former was issued five years earlier than the appearance of the original of Riehl’s book and, naturally, does not contain the new material that the intervening years have provided in abundance, especially in the theoretical respect. N. F. Zhirov’s very valuable book is primarily a chemical manual for the preparation of luminous compositions; physical questions are treated in it only incidentally, in order to complete the description of the properties of the individual classes of compositions obtained. Riehl’s book has a different character: it gives the reader a general physical, experimental, and theoretical survey of the modern theory of the luminescence of crystallophosphors.

Its first, introductory part (pp. 9–29) is devoted chiefly to a description of the methods and apparatus of luminescence measurements. Here the author, in some cases, gives a detailed description, providing useful but by no means specific information for luminescence, such as, for example, the burning characteristics of various gas-discharge lamps, tables of the transmission of Schott light filters, recipes for isolating individual monochromatic lines, etc. On the other hand, specifically luminescence methods—for example, phosphoroscopic ones—are described far from fully.

Further follow Chapters IV–VIII, devoted to the physics of the phenomenon (pp. 29–115). Chapter IV, throughout only 20 pages, describes the properties of the most important inorganic luminophores: zinc and cadmium sulfides, silicates, tungstates and molybdates, sulfides and oxides of the alkaline-earth metals, and, very briefly, certain other luminous substances. The presentation of the luminescence properties of the individual classes of luminophores is extremely compressed. For comparison I note that, for example, in the well-known book by P. Pringsheim (1928), which has a completely different character and is devoted mainly to the luminescence of molecules, this question is nevertheless allotted twice as much space.

Chapters V–VII (pp. 49–115) examine the course of the luminescence of crystal phosphors under various conditions, set forth the theory of these phenomena on the basis of the modern theory of semiconductors, and compare the theory with experiment. These chapters are of the greatest interest. Here an enormous variety of phosphorescence phenomena is arranged into a general scheme, and a certain picture of the phenomenon is given. The presentation is carried out in an extremely subjective manner. The author attaches exceptional importance to his own experiments, often qualitative ones; the extensive material of the world literature is drawn upon far from sufficiently, and in the theoretical treatment of the question it is often ignored.

In the theoretical part the author is likewise very subjective. As direct assertions he advances a number of propositions that are in fact debatable, and sometimes even incorrect. The editors have supplied the book with very valuable notes correcting many of these points, for example, the definition of the very concept of luminescence, and a number of others. In addition to the remarks made by the editors, one may point to the highly controversial treatment of the question of so-called instantaneous luminescence, of the question of temperature quenching, and of the causes of the continuous increase in luminescence brightness with increasing excitation intensity. A full enumeration of all the disputed points is hardly appropriate within the limits of a brief review, but those indicated are sufficient to judge their number and significance.

The last part of the book (pp. 115–169) is devoted to various technical applications of luminescence. This part is likewise written briefly; nevertheless, it can serve as a good introduction to the study of the application of the luminescence of crystal phosphors in various fields of technology. Here the author presents a number of data on cathodoluminescence, on steady-action luminous compositions, on the use of luminophores in daylight lamps, and also for emergency lighting and light masking.

In conclusion it should be said that Riehl’s book, despite its subjectivism, evident shortcomings, and incompleteness, is very valuable: it gives a modern and, from a definite point of view, consistent treatment of the phosphorescence phenomena of a technically very important class of luminescent substances—crystal phosphors. By the nature of its presentation the book is accessible to the nonspecialist; however, when reading it, the specialist must remember that the orderly edifice of the theory of phosphorescence which the author presents to his view as almost complete is in fact still only being constructed, and with the further development of our knowledge will in many respects, and indeed in essential respects, be different from that described by the author.

The book has been published quite satisfactorily. As defects one should note the extremely small type, the very difficult reading, and the incomprehensible placement of all photoreproductions at the end of the book in separate plates. This separation of the text from the figures cannot be justified by the need to print them on special paper, since the paper used for the plates is the same as in the whole book.

V. L. Levshin