LEV VLADIMIROVICH MYSOVSKY

(1888–1939)

IN MEMORY OF LEV VLADIMIROVICH MYSOVSKY

V. G. Khlopin, Leningrad

On August 28, 1939, in the full prime of his scientific activity, after a long and serious illness, Lev Vladimirovich Mysovsky died of paralysis of the heart. He had been head of the Laboratory of Naturally Radioactive Elements of the Radium Institute of the Academy of Sciences of the USSR, head of the Department of Physics of the Agricultural Institute in Leningrad, Doctor of Physical Sciences, and professor.

L. V. Mysovsky was born on February 18 (new style), 1888, in the city of Saratov, into the family of a military physician. His father, Vladimir Manuilovich, served all his life as a military physician—first in Saratov, then in Odessa, and finally in the former Poland. Lev Vladimirovich’s mother, Klavdia Pavlovna, née Beteryakova, came from a highly cultured family, and the rich library she inherited from her father played a major role in the formation of L. V.’s personality.

L. V. received his secondary education at the 3rd Odessa Gymnasium; after graduating from it, in 1907 he entered the Physics and Mathematics Faculty of St. Petersburg University. Already at the gymnasium L. V. had become seriously interested in physics and mathematics and devoted much time to their thorough study. In those same school years there already appeared in L. V. the independence, originality, and simplicity in the posing and solution of individual problems that would later characterize all of his scientific work. Thus, while still at the gymnasium, in geometry he gave a method for the elementary construction of a tangent at any point of an ellipse, and in optics he found a simple solution to the problem of stereoscopic representation of large pictures. The solution of this second problem, given by L. V., proved so interesting that it was demonstrated much later, when L. V. was already a student, at one of the meetings of the Second Mendeleev Congress devoted to students’ work. In 1914 L. V. graduated from the University, having submitted an experimental study “On the Electric Account of α-Particles,” and was retained by Prof. I. I. Borgman at the Department of Physics for preparation for a professorship, but without a stipend, which compelled him, in order to earn a living, to take a position as a physics teacher at a gymnasium.

Teaching physics in secondary school occupied L. V. for four years (from 1914 to 1918) and brought it to a high level. In 1918 L. V. was invited, as a scientific associate and full member, to the Radium Department of the newly founded State X-ray and Radiological Institute, where he was appointed first assistant to the head and then, after the death of L. S. Kolovrat-Chervinsky, head of the department. In 1922, when the State Radium Institute was founded, incorporating the Radium Department of the X-ray and Radiological Institute, L. V. became head of the Physics Department of the Radium Institute, to the organization and development of which he devoted all his strength and his extraordinary talent. The entire scientific activity of the late L. V. Mysovsky, with the exception of his first two works, is inseparably connected with the activity of the Physics Department of the Radium Institute.

Below I shall try briefly to set forth the main results of L. V.’s scientific, pedagogical, and organizational activity, and to sketch his image as a scientist and teacher.

L. V. produced a large number of works, a detailed list of which is given at the end. All of L. V. Mysovsky’s works may be divided into four main groups: 1) works on radioactivity, 2) works on cosmic rays, 3) works on neutrons and artificial radioactivity, and 4) popular-scientific works and manuals. Outside this division stands only one work of L. V., devoted to the interference of X-rays passing through matter with oriented molecules, carried out by him in 1918–1919 and printed in ZhRFKhO in 1923. In this work L. V. extends the simple method proposed in 1915 by Ehrenfest for explaining the interference pattern of X-rays that have passed through a diatomic gas to the case when the number of scattering centers \(n\) is arbitrarily large. In doing so he gives a theoretical calculation of the influence of magnetic orientation on the diffraction pattern.

1. WORKS ON RADIOACTIVITY (1922—1930)

In order to understand the very varied character of L. V.’s works in this field—works that at first glance are not connected by a unity of idea—it is necessary to recall the conditions under which his work proceeded in those years. Having assumed, in 1922, the direction of the Physics Department of the Radium Institute, L. V., under this “grand” name, in fact obtained at his disposal a comparatively large empty space, consisting of several former apartments of professors of the former lyceum, not equipped and not adapted for experimental physical work, and moreover almost devoid of any apparatus. The first years therefore excluded the possibility of setting up any at all complex experimental work and were spent creating, in this empty space, an experimental physics laboratory, which would make it possible—

...in the future to put forward a whole series of subtle and complex works on nuclear physics. It is therefore not surprising that L. V.’s first works in the field of radioactivity, not counting his diploma work, carried out jointly with K. F. Nesturkh on the electrical counting of α-particles, were theoretical rather than experimental works and dealt with the fundamental question of the relation between the energy of α-particles and the radioactive-decay constant. These include three of his works 4, 5, 7. The most interesting conclusion of these works is the probability of assuming the existence of α-particle energy levels in the atomic nucleus. The existence of energy levels in the nucleus is at present accepted by everyone. However, being not a theoretician but an experimental physicist par excellence, L. V. very soon turned to experimental work on radioactivity; moreover, considering that these first works coincided with the organization of production control in the newly born radium industry, on the one hand, and with the organization of laboratories of the Physical Department of the GRI and a practical course on radioactivity in it, on the other hand, he chose as the themes for his work the methodology of radioactive measurements. Thus, in 1924 L. V. Mysovskii published “A New Method for Observing Scintillations.” The scintillation method, along with the Wilson chamber method, was at that time the principal method for the experimental study of charged material particles of high energy (α-particles and protons) and, consequently, one of the cardinal methods for determining radioactive constants and for studying the phenomenon of artificial disintegration of the atom, which had only recently been discovered. It is no accident that L. V. devoted one of his first works to the study and improvement of this method. In this work L. V. proposed replacing the commonly used transparent screen of zinc sulfide with an opaque one, covered with a thick layer of ZnS, placed in front of a silvered achromatic lens on one side, which also serves as the microscope objective. The α-particles causing scintillations pass through a small opening in the objective, and the image produced by the mirror objective is viewed through the eyepiece. This method gives a number of advantages: 1) the efficiency factor of the screen is increased practically to 100%, 2) there is no loss of brightness of the scintillation image when passing through the layer of zinc sulfide, and 3) the brightness of the image given by the objective of a given lens is increased.

In the following year, 1925, L. V. published his compensation method for measuring small quantities of radioactive substances by γ-rays on an electroscope. This method subsequently became widespread for measuring radium and radon preparations in contaminated rooms or near them. Its essence consists in modifying the electroscope construction in a way appropriate to this case, allowing the Rutherford and Chadwick compensation method to be applied to it, using it to determine quantities of radium lying in a very wide interval from 0.1 to \(10^{-8}\) g of Ra element.

V. G. KHLOPIN

In this same work the sources of possible measurement errors and the methods of combating them are examined in detail.

Despite the introduction of substantial improvements into the scintillation method, the latter, apparently, still did not satisfy L. V. Mysovskii; and so, two years later, in 1927, he again returned to the methodology for studying charged material particles of high energy and, together with the student Chizhov, proposed a new method for recording α-particles by means of photographic plates with a thick emulsion layer. This work served as the beginning for the detailed development of a new objective method not only for the qualitative, but also for the quantitative study and continuous recording of charged material particles, which was subsequently carried out in the Physical Department of the Radium Institute under the direction of L. V. Mysovskii by a number of his pupils (Deizenrog-Mysovskaya, Laptev, Zhdanov, and others). At the present time this method has attained, in Zhdanov’s works, such a degree of perfection that, in its importance for the study of nuclear transformations, it must be placed no lower than the Wilson chamber method, and in some cases it has even greater advantages over the latter. In this work of 1927, perhaps more than in all the others, there appears that feature of the late L. V. which, as I have indicated, was characteristic of him and which manifested itself in him even in his student years—namely, simplicity in the solution of the questions posed. Indeed, the idea of the photographic method proposed by L. V. is extremely simple, and after it has been expressed one may wonder that it had not long before been expressed by investigators working with the photographic method (especially if one takes into account that the photographic method was the first method applied to the study of radioactive radiations).

In fact, what was the principal shortcoming of the photographic method? It was that it is essentially a planar method, whereas all phenomena of nuclear transformations occur in space. And so L. V. proposed to make this method spatial in a simple way: to create a layer of light-sensitive emulsion such that all nuclear transformations would take place within this layer, and, in studying the traces left by these transformations, to apply the method of microstereophotography. Both these ideas immediately justified themselves in the very first work published by L. V. jointly with Chizhov, and proved so fruitful that, in a series of subsequent works carried out under L. V.’s direction, they made it possible to transform a method that seemed already consigned to the archives into a powerful instrument for the experimental study of nuclear transformations. I think I shall not be mistaken in saying that if L. V. had given physics nothing besides the work discussed above, even then he, as the creator of the method of thick-layer photographic plates, would forever have entered physics, especially nuclear physics. At the present time this is indisputable, but at first the experimental difficulties in the preparation of thick-layer

In Memory of Lev Vladimirovich Mysovskii

plates for a long time hindered the use of the method proposed by L. V. in foreign laboratories, and only comparatively recently, after 1935, did it begin to acquire ever wider and wider dissemination; however, even up to the present time the technique of this method abroad lags far behind the technique that was developed in the laboratory of Lev Vladimirovich Mysovskii.

It is interesting to note that as early as 1932, at the 1st All-Union Conference on Radioactivity, the late L. V. quite correctly indicated also that field in which this method would in all probability prove irreplaceable—namely, the study of cosmic rays and of the processes that they cause.

In order to conclude the review of L. V.’s work on radioactivity, I have still to mention two of his works in this field: the application of the Wilson chamber to the study of the $\beta$-rays of rubidium, carried out jointly with R. A. Eikhelberger, and the new method proposed by him for the radiographic examination of metal castings by means of the $\gamma$-rays of radium, with the aim of detecting in them blowholes and other defects. I should like to dwell somewhat on this latter work, carried out by L. V. jointly with T. S. Izmailova as early as 1926, since it was the first swallow that marked the beginning of a series of studies in this field, conducted in Germany, the USA, and other countries, and opened up a new broad field of application for the $\gamma$-rays of radioactive substances. In this work of his, L. V. proposes, in those cases where the thickness of the metal being examined is large, to use the $\gamma$-rays of radium instead of X-rays, and, in order to shorten the exposure time, to use instead of photographic plates or films an electroscope or electrometer operating by the compensation method. This same work indicates the principal procedures for determining the depth of occurrence and the dimensions of a flaw. The new method proposed by L. V. as early as 1926 only considerably later, approximately in 1930–1931, began to spread abroad, and even at the present time not everything given in this small work has been used to the proper extent. Thus, for example, the attempt to replace the photographic method by the ionization method is only just beginning to be carried out.

2. Works of L. V. Mysovskii on Cosmic Rays

(from 1925 to 1939)

L. V. Mysovskii was the first physicist in our Union to undertake, in 1925, the study of cosmic rays, which before him had completely fallen out of the field of vision of Russian physics, and his works in this field enjoy well-deserved renown. In order to assess more correctly the significance of L. V.’s works in the field of cosmic rays, it is necessary to recall the state of the question concerning cosmic radiation and its properties by the beginning of L. V. Mysovskii’s work. Cosmic radiation was discovered in 1912 by Hess and, soon after him, by Kolhörster, who gave for it in his summary of 1923 an absorption coefficient in water equal to $2.3 \cdot 10^{-3}\ \mathrm{cm}^{-1}$. However, in the same year, 1923, in the autumn, at

V. G. KHLOPIN

The famous American physicist Millikan took up the study of cosmic radiation; he found that the absorption coefficient of this radiation is practically identical with the absorption coefficient of the $\gamma$-rays of radioactive substances. These data were published in the summer of 1924 and called into question the very existence of cosmic radiation. It was at this very moment that L. V. Mysovskii, together with L. R. Tuwim, began studying cosmic rays and, in a series of papers (five in number), unquestionably proved the existence of penetrating cosmic radiation and determined the (total) absorption coefficient of these rays in water, which turned out to be equal to $2.8 \cdot 10^{-3}\ \mathrm{cm}^{-1}$, i.e., more than ten times smaller than the absorption coefficient for the $\gamma$-rays of RaC and ThC (1925). Further, by specially designed ingenious experiments in the following year, 1926, L. V. Mysovskii proved that penetrating radiation comes to us from above, from celestial space, uniformly from all directions, and that its intensity does not depend on azimuth in middle latitudes. In the same year, 1926, L. V. discovered interesting temporal fluctuations in the intensity of cosmic radiation and showed that these fluctuations depend on atmospheric pressure. In the following year, 1927, again studying the absorption coefficient of cosmic rays in water and lead, he discovered the effect of a transition layer. He attributed this effect to the absorption of secondary radiation accompanying the primary cosmic radiation and produced when the primary radiation passes through a material medium. In this work L. V. gives the value of the wavelength both for primary and for secondary rays. For the former it was found to be $4.4 \cdot 10^{-4}\ \text{Å}$, while for the latter it practically coincided with the wavelength of the $\gamma$-rays of RaC. L. V., however, did not attach special significance to this latter value, considering this coincidence accidental and pointing out that, in order to calculate $\lambda$ for the secondary radiation, one should study absorption in the transition layer for the most varied substances.

Thus, in this series of works L. V. not only gives rigorous proof of the presence of cosmic radiation at a moment when the existence of this radiation was being called into doubt, but also establishes a number of fundamental properties of it.

After 1928 there comes a long interruption, during which L. V. himself did no experimental work on the study of cosmic rays; however, even during this period, on his initiative and partly under his direction, work was carried out by the postgraduate student S. N. Vernov on the study of cosmic rays at great altitudes (on balloon-sondes) using Geiger–Müller counters, with the operation of the counters transmitted by radio to the ground. From 1934 L. V. himself turned to the study of cosmic rays by the Wilson chamber method and in 1934, together with Eigenson, published a paper on the observation of neutrons from cosmic rays. In the very last period, shortly before his death, he completed, but unfortunately did not have time to process, a very interesting work in which he succeeded in observing the emergence of electrons at the end of the path of

charged material particles, and the direction of the electron’s path most often coincides with the direction of the path of the material particle. It is to be hoped that the results obtained by L. V. will be processed and published by his closest students in the near future.

3. WORKS OF L. V. MYSOVSKY ON NEUTRONS AND ARTIFICIAL RADIOACTIVITY (1934–1939)

To this series of works, in addition to the investigations proper on artificial radioactivity and artificial radioelements, I also assign the work of L. V. Mysovsky carried out by him jointly with V. N. Rukavishnikov in 1922 on “the acceleration of positive and negative ions by a high-frequency alternating-current field.” The task of this work included finding a method for artificially obtaining a beam of ions with very high energy for the purpose of acting with them on matter, i.e., as we would now say, in order to cause the splitting of the atomic nucleus and obtain artificial radioactivity. At the beginning of the twenties not a single investigator attempting to develop a method for obtaining artificial radioactivity would have ventured to give such a title to his work in advance; it is not surprising that L. V., too, gave his joint work with V. N. Rukavishnikov a much more modest title. In this investigation L. V. for the first time indicates an ingenious and simple device that makes it possible simply and conveniently to introduce a very high voltage inside an evacuated glass vessel—the creation of a standing wave with an antinode of potentials at the end of a spiral remote from the lead-in—and describes the principal phenomena that take place in the tube under these conditions. Later V. N. Rukavishnikov, under the direction of L. V., studied in detail the conditions of operation of such a tube and clarified the role of ohmic resistance in the Tesla-transformer regime. The construction of a large installation for accelerating ions, based on the Tesla-transformer principle, encountered great technical difficulties in our country; however, in America, admittedly many years later, in 1932, the physicists G. Breit, M. Tuve, and O. Dahl carried out the construction of such an installation.

From 1922 to 1934 no experimental works by L. V. appeared in this direction; from 1934 onward, after the discovery of artificial radioactivity by the Joliot-Curies and Fermi, L. V. published a number of works on the properties of neutrons and their action on the nuclei of chemical elements. Almost all these works were produced jointly by two institutes—the Radium and the Physico-Technical—and, as such, each was carried out by an entire mixed team of no fewer than four collaborators. Of these works, eight in all, two concern the properties of neutrons—these are the work on the scattering of neutrons in water and in lead and on the energy of neutrons and the Fermi effect; the rest are devoted to the study of nuclear reactions and artificial radioactive elements. Of greatest interest to us from this cycle of works are: 1) the work in which a new radioactive

isotope of bromine with a long period; 2) work on the continuous spectrum of β-rays from bromine with a half-life of 36 hours (according to observations in a Wilson chamber); 3) work indicating the possibility of the disintegration of nuclei by neutrons with the emission of three heavy particles; and 4) work on the scattering of neutrons in water and lead, because in these works, apparently, the undoubtedly outstanding role was played by the late L. V., whereas in the other joint works, not having taken part in them, it is very difficult for me to judge the relative weight of the individual workers. What grounds make me think that in the four works indicated above the outstanding role was played by Lev Vladimirovich himself? With respect to three works (2, 3, and 4) this apparently admits of no doubt, since the participants in the works themselves violated the usually established alphabetical order of authors and put Mysovsky’s surname in first place; in the fourth case (1), where this was not done, my personal observations allow me to judge the great role of L. V. I shall begin with the last work. I remember how once, already at night, I found L. V. studying in a Wilson chamber the radiation of artificially radioactive bromine, and how he shared with me the remarkable observation that an old preparation of radiobromine, which should already have practically decayed completely, was displaying a noticeable activity, the change of which he intended to trace. As we all now know, this observation of L. V.’s was entirely correct and led, in further investigations, to the establishment of the presence of a third, longer-lived radioactive isotope of bromine. At the same time, historically, this discovery of a third isotope of bromine was the first case of nuclear isomerism. Thus this work not only led to the discovery of a new artificial radioactive isotope, but also, what is far more interesting, led to the discovery of nuclear isomerism, which was then established in a number of other cases and opened up a new field of extremely interesting theoretical as well as experimental investigations. The work on the continuous β-spectrum of the long-lived isotope of bromine is interesting in that in it, for the first time by the Wilson-chamber method, the energy distribution in the spectrum of bromine with \(T = 36\) hours was obtained, agreeing well with those obtained by the Geiger–Müller counter method by the Alikhanov brothers for the same element.

Of great interest is the third work of L. V., in which several cases are described for the first time of nuclei being split by neutrons with the emission not of one, as usual, but of three heavy particles. Reactions of this kind, described then for the first time, are now widely known, chiefly under the action of cosmic neutrons and quanta of cosmic rays on the nuclei of chemical elements.

In concluding the survey of L. V.’s scientific-research works, I should like to point to two of his joint works with A. P. Zhdanov, in which the method of thick-layer photographic plates was first applied to the study of the newly discovered phenomenon

of the fission of the uranium atom nucleus. In this work the authors introduced uranium into the emulsion itself, and in this way they succeeded in observing very clearly the tracks of fragments of the uranium nucleus and in establishing that they have different effective charge and mass.

4. TEXTBOOKS AND POPULAR-SCIENTIFIC WORKS OF L. V. MYSOVSKY

L. V. was not only a major and original researcher, but also an excellent popularizer and teacher. He was able to present very difficult questions very intelligibly and vividly. This characteristic of his was noticed and highly appreciated by such a master of exposition as the late Orest Danilovich Khvolson. Of the numerous review and popular-scientific articles and monographs I shall dwell here only on three, namely: 1) on his monograph Cosmic Rays (1929), which was the first summary in Russian of our knowledge of cosmic rays; this little book, for the clarity of its exposition, received very high praise from O. D. Khvolson. 2) Then on his book New Ideas in the Physics of the Atomic Nucleus, which is an excellent, clear, and very interesting and simply written survey in this field, now appearing in its third edition at the publishing house of the Academy of Sciences. This book may be recommended for reading to all who wish to become acquainted with the new views and discoveries in this rapidly developing branch of physics and, at the same time, as a manual for initial study. 3) Finally, one cannot pass over in silence the course of electricity for higher educational institutions (1933), written by L. V. in a very original and clearly structured manner.

Our account of the activity of the late L. V. Mysovsky would be incomplete if we did not dwell briefly on him as a teacher and organizer.

5. PEDAGOGICAL AND ORGANIZATIONAL ACTIVITY OF L. V. MYSOVSKY

The pedagogical activity of L. V. Mysovsky began, as we have already indicated, immediately after his graduation from the university, i.e. in 1914, and during the first four years took place in secondary school, and then passed on to higher education. From 1922 L. V. taught and directed the physics laboratory at the Leningrad Polytechnic, now Industrial, Institute. In 1931 L. V. organized at Leningrad University a new specialty in radiology and headed the department of radiology. During the years from 1931 to 1936, L. V., as head of the department in this specialty, trained numerous cadres of highly qualified young specialists. The most capable of them then went on—and some are still going on—to postgraduate study at the Radium Institute of the Academy of Sciences of the USSR. Finally, from 1936 L. V. occupied the chair of physics at the Leningrad Agricultural Institute. In all places where L. V. taught, the specialists trained by him not only

acquired thorough knowledge of physics, but also caught fire with an aspiration toward scientific-research work. This explained why the Radium Institute drew the personnel for its physicists from all the places where L. V. carried on his pedagogical work. Besides his work in higher education, L. V. also conducted extensive pedagogical work within the walls of the Radium Institute, where he organized a special practicum in radioactivity, through which about 300 people passed during the time of its existence.

The organizational activity of L. V. Mysovskii was also very varied and successful. First of all, from 1922 he organized the Physics Department of the Radium Institute, and from 1925 also the special radon laboratory attached to it, which began supplying medical institutions with radium emanation preparations. To replenish the Physics Department with various precise instruments, L. V. was twice sent abroad; on one of these trips he compared the radium standards prepared by us with international ones. Properly recognizing the impossibility of the Physics Department’s work without a good scientific-experimental workshop, L. V. from the very beginning devoted much effort to creating mechanical and glassblowing workshops at the Radium Institute and to equipping them. Finally, from 1933 L. V. took the initiative in creating at the Radium Institute the first Soviet cyclotron; together with his closest collaborators—V. N. Rukavishnikov, D. G. Alikhanov, and others—he placed orders for the various parts of the installation, supervised their manufacture and testing. The creation of the first Soviet cyclotron was associated with great difficulties of both a technical and an organizational nature, which, thanks to L. V.’s energy and persistence, were overcome; and at the present time we already see the first Soviet cyclotron in operation and can judge the first results of work with it. Premature death prevented L. V. from making full use, for his creative scientific-research work, of the installation to whose creation he had devoted so much energy and knowledge and which prematurely undermined his strength.

Along with the organization of the Physics Department of the Radium Institute, in 1931 L. V., as we have seen, organized the Department of Radiology at Leningrad University; in 1933 he organized the nuclear group of the Steklov Physico-Mathematical Institute of the Academy of Sciences of the USSR, later, with the transfer of the Academy to Moscow, developed into the nuclear laboratory of the Physical Institute of the Academy of Sciences of the USSR; and, finally, in 1936 he reorganized the Department of Physics at the Leningrad Agricultural Institute. At the same time L. V. directed the work of all the institutions organized by him.

With this I shall conclude my brief sketch of the activity of the late L. V. Mysovskii, in which I have tried to portray him as a scientific researcher, teacher, and organizer.

Premature death has torn from our midst an original and brilliantly learned man, a talented teacher, and a major organizer, whose loss will be keenly felt by Soviet science.

LIST OF PRINTED WORKS BY L. V. MYSOVSKY

1. On the electric charge of $\alpha$-particles, ZhRFKhO, 45, 149, 1913.
2. Stossweise Spitzenstromentladungen u. elektrische Methode d. Zählung d. $\alpha$-Teilchen, Ann. d. Phys., 4, 461, 1914.
3. Interference of Roentgen rays passing through matter with oriented molecules, ZhRFKhO, 55, 18, 1923.
4. Derivation of a formula relating the radioactive decay constant to the energy of $\alpha$-particles, DAN, p. 41, 1922.
5. Regularity of the distribution of energy among $\alpha$-particles of radioactive elements, DAN, p. 55, 1922.
6. Acceleration of positive and negative ions by a high-frequency alternating-current field (jointly with V. N. Rukavishnikov), DAN, p. 53, 1922.
7. Ueber den Zusammenhang zwischen d. $\alpha$-Teilchen u. d. Atomnummern der Elemente, Z. Physik, 18, 304, 1923.
8. Observation of scintillations on an opaque screen by means of a microscope with a mirror objective, DAN, p. 155, 1924.
9. Versuche über die Absorption d. Höhenstrahlung im Wasser (L. Myssowsky u. L. Tuwim), Z. Physik, 35, 299, 1925.
10. Measurement of small quantities of radioactive substances by the electroscopic method using $\gamma$-rays, ZhRFKhO, 57, 1, 1925.
11. The State Radium Institute and its activity, Priroda, No. 7/9, 218, 1925.
12. Unregelmässige Intensitätsschwankungen d. Höhenstrahlung in geringer Seehöhe (L. Myssowsky u. L. Tuwim), Z. Physik, 39, 146, 1926.
13. Versuche über die Richtung d. Höhenstrahlung im Meeresniveau (L. Myssowsky u. L. Tuwim), Z. Physik, 36, 615, 1926.
14. On work on the study of penetrating radiation (jointly with L. R. Tuwim), DAN, p. 26, 1926.
15. Transillumination of metallic castings with the $\gamma$-rays of radium for the purpose of detecting cavities and other defects in them (jointly with T. S. Izmailova), DAN, p. 29, 1926.
16. Absorptionskurve d. Höhenstrahlung im Wasser (L. Myssowsky u. L. Tuwim), Z. Physik, 44, 369, 1927.
17. Absorption in Blei, sekundäre Strahlen u. Wellenlänge d. Höhenstrahlung (L. Myssowsky u. L. Tuwim), Z. Physik, 50, 273, 1928.
18. Spuren der $\alpha$-Teilchen in dicker Bromsilbergelatineschicht der photographischen Platten (L. Myssowsky u. P. Tschischow), Z. Physik, 44, 408, 1927.
19. Work of the Radium Institute on the study of cosmic radiation, Priroda, No. 4, 330, 1928.
20. Cosmic rays, Gosisdat, 1928.
21. Study of the nature of cosmic rays, Priroda, No. 6, 494, 1929.
22. Cosmic rays, Man and Nature, No. 1, 1929.
23. Improvement of observations of $\alpha$- and $\beta$-particles, Advances in the Physical Sciences, 9, 574, 1930.
24. Experimental study of the nature of cosmic rays, Advances in the Physical Sciences, 10, 1, 1930.
25. New investigations on the nature and origin of cosmic rays, Nauchnoe slovo, 1930.
26. Rubidiumstrahlen in d. Wilsonschen Nebelkammer (L. Myssowsky u. R. Eichelberger), DAN, No. 24, 652, 1930.
27. New paths toward the study of the nature of cosmic rays, Advances in the Physical Sciences, 12, 625, 1932.
28. Laboratory method for obtaining high potentials, Advances in the Physical Sciences, 10, 545, 1930.
29. Laboratory methods for obtaining fast electrons and protons, Advances in the Physical Sciences, 12, 580, 1932.
30. General course of physics for higher technical educational institutions, Part II, issue 1. Electricity, ONTI, 1933.

1. Passage of cosmic rays through matter, Uspekhi fizich. nauk, 13, 518, 1933.

2. Organization and development of the State Radium Institute, in: Collection: Universities and Scientific Institutions for the XVII Party Congress, Tekhteoret, p. 294, 1934.

3. Observation of neutrons from cosmic rays in a Wilson chamber (jointly with M. Eigenson), DAN, 2, 221, 1934.

4. New Ideas in the Physics of the Atomic Nucleus, Publishing House of the Academy of Sciences of the USSR, 1935.

5. A historical survey of the development of the doctrine of cosmic rays in connection with research at high altitudes, Proceedings of the All-Union Conference on the Study of the Stratosphere, Publishing House of the Academy of Sciences of the USSR, 389, 1935.

6. The Fermi effect in phosphorus (jointly with I. Kurchatov, G. Shchepkin, and A. Vibe), DAN, 3, 221, 1934.

7. The Fermi effect in aluminum (jointly with I. V. Kurchatov, B. V. Kurchatov, G. Ya. Shchepkin, and A. Vibe), DAN, 3, 422, 1934.

8. The possibility of nuclear disintegration by neutrons with the emission of three heavy particles (jointly with I. Kurchatov, N. Dobrotin, and I. Gurevich), DAN, 3, 230, 1934.

9. Sur un cas de radioactivité artificielle provoquée par un bombardement de neutrons, sans capture de neutrons (jointly with V. Kurchatov, I. Kurchatov, and L. Rusinov), C. R., 200, 1201, 1935.

10. The Fermi effect, Priroda, No. 6, 23, 1935.

11. The Energy of Neutrons and the Fermi Effect (jointly with I. Kurchatov, G. Shchepkin, and M. Eremeev), Sow. Phys., 7, 257, 1935.

12. Au sujet de la capture de neutrons lents par un noyau (jointly with L. Artsimovich, I. Kurchatov, and P. Palybin), C. R., 200, 2159, 1935.

13. Ueber Neutronenstrahlung in Wasser und Blei (jointly with M. Yu. Deisenroth-Mysovskaya, I. Kurchatov, and G. Latyshev), Sow. Phys., 7, 646, 1935.

14. New Ideas in the Physics of the Atomic Nucleus, 2nd enlarged edition, Publishing House of the Academy of Sciences of the USSR, 1936.

15. Artificial radioactivity, “SORENA,” No. 6, 10, 1936.

16. Continuous spectrum of γ-rays from bromine with a half-period of 36 hours (jointly with I. Kurchatov, R. A. Eichelberger, and G. Latyshev), Jubilee Collection Dedicated to the 50th Anniversary of the Scientific Activity of Academician V. I. Vernadsky, Publishing House of the Academy of Sciences of the USSR, 2, 547, 1936.

17. Transmission of γ-rays, Roentgenography as Applied to the Study of Materials, NKTP—NIS—Tekhprop, 1936.

18. New Ideas in the Physics of the Atomic Nucleus, Publishing House of the Academy of Sciences of the USSR, 1938 (3rd enlarged edition submitted for publication).

19. Tracks on Photographic Plates of the Recoil Nuclei of Desintegration of Uranium, Nature, 143, 794, 1939.

20. Tracks of recoil nuclei in the splitting of uranium by neutrons (jointly with A. P. Zhdanov and M. Yu. Mysovskaya), DAN, 23, 341, 1939.

21. Observation of the fission of uranium nuclei placed inside emulsions of thick-layer photographic plates and subjected to neutron bombardment (jointly with A. P. Zhdanov), DAN, 25, 9, 1939.