by Igor SILKIN,

Director of the Zavoisky Memorial Laboratory, Kazan (Volga Region) Federal University (Kazan, Tatarstan)

In 1994 an exhibition of physical instruments of the 19th-early 20th centuries took place at the International AMPERE Congress. It was devoted to the 50th anniversary of the discovery of electron paramagnetic resonance (EPR), with Kazan State University as the host. For one, it featured a unique exhibit: a working setup for observing the absorption effect of a radio-frequency field described in the doctoral thesis of the experimental physicist Yevgeny Zavoisky. Using this setup, he made a pioneering discovery in 1944, thus laying the foundation for a new dynamic area in modern physics, the magnetic radio spectroscopy. The Kazan exhibits aroused genuine interest among Russian and foreign participants. They came up with an idea of a memorial laboratory in the university. Three years later its directorate set aside lecture room 253 (today 246), where EPR had been discovered, for this purpose.

For Kazan University the name of Zavoisky* in physics is as meaningful as the name of the creator of non-Euclidean geometry (1826) Nikolai Lobachevsky in mathematics, the author of the theory of the organic compound structure (1861) Alexander Butlerov in chemistry and linguist and Slavicist Jean Baudouin de Courtenay in philology. A member of the national Academy of Sciences, a Stalin (1949) and Lenin Prize (1957) winner and Hero of Socialist Labor (1969), Zavoisky was born in Mogilev-Podolsk of the Vinnitsa Region (Ukraine) in 1907. Almost forty years of his life were associated with Kazan, a city on the Volga. His family moved there in August of 1908. First he attended a three-grade primary school (1915-1917) and then the

* See: V. Popov, "A Pioneer in Paramagnetic Resonance", Science in Russia, No. 6, 2008.--Ed.

new school No. 10 at Zarechensk. He continued his studies in the town of Slobodskoy on the Vyatka River, where the family moved after his father died. In 1925 Zavoisky returned to Kazan and upon completing a course at a nine-grade school, got enrolled in Kazan University in 1926, one of the oldest in Russia, established by Emperor Alexander I in 1804. A college student and postgraduate, Candidate of Sciences (M. Sa), Doctor of Sciences (Phys. & Math.) and the pathfinder of the electronic paramagnetic resonance phenomenon--such were the milestones of the Kazan period of his scientific work reflected in numerous exhibits, archival documents and materials of the memorial laboratory. It should be noted that the Zavoisky Memorial Laboratory is the youngest among several other museums at Kazan University, namely, the museum of history, its chemical school, as well the museums of astronomy, ethnography, archeology, geology, zoology and botany.

The idea of the memorial laboratory came up well before the International Ampere Congress. On Zavoisky's initiative, in 1975, his self-made facilities and instruments of the late 1950s were brought from Moscow to Kazan. But the equipment, which he used in search of nuclear magnetic resonance (NMR) signals in the spring of 1941, and the electronic paramagnetic resonance setup of 1943-1944, at which the experimentalist observed this phenomenon for the first time, were lost. Professor Semyon Altschuler (corresponding member of the USSR Academy of Sciences), head of the magnetic radio spectroscopy department, suggested that I, then a student of the Physico-Mathematical Department, should get busy with their reconstruction. Since Prof. Altschuler saw that this task could not be solved without a detailed study of the diary notes and recollections of Zavoisky's co-workers, his personal documents and university archives, and a detailed knowledge of the equipment of that time, he recommended that I should study first Zavoisky's research record at Kazan University and the history of electronic paramagnetic resonance.

Thus started the 15-year work in search of electric and radio-measuring instruments of the 1930s and 1940s, and of materials in libraries, archives and museums, research institutes and educational institutions, in particular, at Kazan University, the Academy of Sciences of the Republic of Tatarstan and its National Archives, the Kapitza Physical Research Institute (Moscow) and the USSR Academy of Sciences.

It became possible to find some rare instruments, such as the low-frequency amplifier used by Zavoisky in 1943-1945 and incorporated into the Abbot profile meter, an American instrument for surface roughness assessment and the oscillograph Triumph used in the experiments of 1946-1947. Also found were other instruments used by Zavoisky in his lectures on physics in Kazan University. The search for the original equipment he worked with covered not only Kazan university but also the Aeronautical, Medical, Teaching, Agricultural and Veterinary Institutes of Kazan, the city school No. 131, the aircraft works No. 16 and private collectors as well.

Collecting personal books of the scientist and the literature mentioned in his archival notes proceeded simultaneously. These materials included reminiscences of his colleagues and contemporaries, in particular, Professor Boris Kozyrev of Kazan State University (corresponding member of the USSR Academy of Sciences) and Semyon Altschuler; together with them Zavoisky studied the physical and chemical action of ultrashort waves. Reminiscences of his close relatives, his daughter Natalia (a scientist) and his brother Vyacheslav were featured prominently in this collection.

Exhibitions and publications were prepared on the basis of research done, including reports at conferences and annual readings in memory of Zavoisky.

The museum was opened on September 28, 1997, on the day of the 90th birth anniversary of the scientist. Its interiors take us back to the 1930s and 1940s as reconstructed from records of those years. Not only laboratory equipment was restored but also the old oak parquet floor, windows, doors, walls, ceiling and lighting fixtures. The exposition shows how the scientist drove his success home. A chronological table was made up with a detailed (day by day) description of his scientific work from 1926 to 1947.

Let's recall some of the milestones on the way toward his main discovery. Zavoisky concerned himself with experiments from his childhood. "I assembled my first electrical bell and electrical friction machine when I was seven years old and could not read yet," he recalled. "Later on came the passion for amateur radio."

In his school hobby group of the town of Slobodskoy he learned the ABC of radio engineering. He assembled his first crystal receiver there and visited a radio station still under construction for reception and transmission of telegrams to the city of Vyatka. Coming back to Kazan, Zavoisky went on with his overriding hobby. He assembled a rather powerful tube radio set and installed an aerial on the house roof.

In his final school years Zavoisky amassed sound knowledge in physics and radio engineering and was all set to enroll in the Physico-Mathematical Department of Kazan University. As a second-year student he

received a patent for his invention of a remote control device for machinery composed of parallel disks equipped with electrical contacts. The principle of this device was as follows. A radio signal activated the clock mechanism or the electric motor causing the disks to rotate relative to each other at a definite angle depending on the length of the signal. The contacts came in touch, and a command was transmitted through a system of levers and electric magnets to the actuator.

Zavoisky designed and built other devices as well. He assembled a secret telegraph and an automatic key to it, as well as a device for the transmission and reception of color static images by radio and wire, and made experiments with selenium and mercury for creating a radio signal amplifier. An exposition on his school and student instrumentation is now at the preparatory stage.

His first serious scientific work, "On Gas-Electric Analogies", was published in May of 1929 in the journal Herald of the Lobachevsky Student Physico-Mathematical Group at Kazan University. Its objective was to identify a gas driving force for liquid bodies, such as water-kerosene and water-vegetable oil pairs. It was an attempt at an independent study of the phenomenon discovered in the early 1920s by the Soviet physicist Iosif Kosonogov (member of the Ukrainian Academy of Sciences). But Zavoisky proceeded further and studied this effect both for solids and for liquid bodies. His work was highly appraised by the Physics Department head Vsevolod Ulyanin (1863-1931).

Upon graduation from Kazan University in 1930 Zavoisky enrolled in postgraduate studies and was sent to the Central Radio Laboratory in Leningrad, where he studied a superregenerative radio receiver in the ultrashort wave laboratory with the help of Professors Georgi Ostroumov and Nikolai Tsiklinsky. At the same time, he worked (together with laboratory worker Pyotr Vinnik) on an in-phase ultrashort-wave oscillator. This work was basic to his postgraduate thesis on the superregenerative effect and its theory maintained in 1933. Unfortunately, its original was not available, but the text was restored with the aid of rough copies and the review of Professor Alexander Shipchinsky.

Thereafter Zavoisky was appointed acting head of the Physics Department of Kazan University. In his newly established ultrashort wave laboratory Zavoisky studied the phenomenon of electromagnetic field absorption by substance using the so-called grid current method of current change on grid and anode at loading the generator's oscillator circuit in which the investigated substance was placed. One of the self-made ultrashort-wave oscillators used by the scientist in such experiments in 1936 was found in the meridian circle of the Engelhard Astronomical Observatory (Republic of Tatarstan). Now this oscillator is one of our museum's rarities.

Zavoisky combined his experimental work with teaching. Under his direction a newly established physical workshop and new laboratories were opened in the university. Some of the exhibits purchased at that time are kept in the museum. Among them are the Dolezalek quadrant electrometer for electric potential measurement, the Nobili astatic galvanometers and the Faraday gas-discharge tube manufactured by German, French and British companies.

Upon taking his candidate's (M. Sc.) degree in physics and mathematics in 1938, Zavoisky set to work at his doctoral thesis on experimental and theoretical studies of some phenomena in high-frequency electric and magnetic fields, in which he was out to sum up practically all

his previous research works on this subject. However, he failed to defend this thesis for reasons unknown to us.

In 1941, he extended the useful frequency range getting ever deeper into the problem of electromagnetic radiowave absorption. It should be noted that physicists turned to this physical phenomenon in the early 1930s. The basic research work in this field belonged to foreign scientists Cornelius Goiter (the Netherlands), Isidor Rabi (USA) and others. Besides, Zavoisky took a special interest in Goiter's works--Goiter used the colorimetric (hot-wire) method in search of nuclear paramagnetic resonance. But Goiter never obtained the desired results. In order to spot nuclear magnetic resonance (NMR) Zavoisky decided to use the more sensitive grid current method he had developed.

The reports on the work of the Physical Department in 1941 with notes about the beginning of experiments in this field were found in materials of the State Archives of the Republic of Tatarstan. Zavoisky's copybook with his notes dating back to the spring and summer of 1941 survived, too. We are certain that even at that time he tried to detect the phenomenon of nuclear magnetic resonance. However, the outbreak of the Great Patriotic War in 1941 made Zavoisky scale down these studies and turn to national defense objectives. He joined the laboratory of Vladimir Arkadiev (corresponding member of the USSR Academy of Sciences), where he invented a new ultra-Hertzian wave transmitter.

Only in 1943 could Zavoisky resume his nuclear magnetic resonance research. As we found out, Kazan University recommended him for the Stalin doctorate, but Moscow did not approve this proposal. On that day as his candidacy was turned down, Zavoisky resumed work on determining nuclear magnetic moments by using more sensitive instrumentation and the modulation method. Early in 1944 he discovered resonance signals in weak magnetic fields (~ 10 Oe) on the 30 m wavelength of a radio-frequency field (10 MHz), but the frequencies and fields were not in agreement with parameters of the nuclear magnetic resonance effect. When he discussed the problem with the head of the Physics Department of Kazan University Yakov Frenkel (corresponding member of the USSR Academy of Sciences), they agreed that in that case the phenomenon of the electronic paramagnetic resonance was observed. We determined the exact date of that event, January 21, 1944.

In the spring of 1944 Zavoisky finished his doctoral thesis on paramagnetic absorption in perpendicular and parallel fields for salts, solutions and metals and sent it to Moscow late in June. Frenkel wrote in his review of the thesis: "Assistant professor of Kazan University Yevgeny Zavoisky has long outgrown the candidate's [M. Sc] degree in physics and mathematics, and in his scientific and educational competence, the modest position of an assistant professor. He is a talented physicist well versed in different fields of experimental and applied physics

(especially in radiophysics and the oscillations theory), capable of solving extremely challenging experimental problems, often with very limited means available. An eloquent proof of his extraordinary experimental abilities is furnished by his doctoral thesis, in which he describes his method of magnetic loss measurement via reaction on a generator of high-frequency oscillations, the method which is hundred times more sensitive than those used before and which enabled the author to obtain new, very interesting experimental results related to the magnetic properties of atoms, ions and electrons in paramagnetic bodies."

At the end of 1944 Zavoisky was invited to a session of the All-Union Scientific Council for Radiophysics and Radio Engineering at the Physics and Mathematics Division of the USSR Academy of Sciences, which was held in the conference hall of the Moscow Physics Institute (FIAN). However, according to the available documents, the delegates did not understand and did not approve his report on the paramagnetic relaxation. "It cannot be," was their verdict. The director of the Institute of Physical Studies of the USSR Academy of Sciences, Nobel Prizewinner (1978) Academician Pyotr Kapitza suggested that Zavoisky should carry out experiments in his institute, and he, Zavoisky, did so prior to the defense of his doctoral thesis that took place on January 30, 1945, at FIAN. The news of these successful Moscow experiments on electron paramagnetic resonance leaked into the press in 1945, and so one came to think that Zavoisky discovered the effect of electron paramagnetic resonance in Moscow.

Back in Kazan, Zavoisky resumed his research work. In his last paper of that period, "On the Theory of Paramagnetic Relaxation in Perpendicular Fields" published in 1947, he analyzed data for salts Mn²⁺ and Cr³⁺ in the crystalline state and in solutions at different frequencies. Zavoisky together with Kozyrev and Altshuler came to an important conclusion: the width of a paramagnetic resonance line is determined, first of all, by magnetic dipole-dipole interactions and can be transformed under the action of exchange forces and splitting of spin levels of paramagnetic ions in an electric field of the surrounding particles.

By decision of the Central Committee of the Communist Party (August 1947), Zavoisky was transferred for permanent work in Moscow and later, to the top secret Arzamas-16 nuclear center* (in the Gorky Region) to take part in the nuclear bomb project. Meanwhile his Kazan colleagues proceeded with the research initiated by him. Thus, for the first time they observed paramagnetic resonance in free radicals and later on discovered the action of a nuclear spin (quantity of motion) of a paramagnetic atom on electron paramagnetic lines.

In the autumn of 1956 the Scientific Council of the Institute of Physical Studies recommended Zavoisky's research works of 1944-1945 for the Lenin Prize. As Academician Pyotr Kapitza wrote in his recommendation "The discovery of paramagnetic resonance is a

* See: V. Lukyanov, "A 'Nuclear Hermitage' at Sarov", Science in Russia, No. 3, 2009.--Ed.

breakthrough that exerted a significant effect on the development of physics in the post-war time".

On April 22, 1957, the next day after an official communication about the award was published, Kapitza sent a cable to Zavoisky: "I congratulate you cordially on your Lenin Prize marking your major discovery worthy of official recognition many years ago. I wish you success in your work. Sincerely yours, Kapitza." Later he wrote that "Zavoisky's discovery should be in for a Nobel Prize". A quarter century later, on June 23, 1970, Zavoisky's discovery was entered in the state register with the priority of July 12, 1944. This date is considered the official "birthday" of electron paramagnetic resonance. Today the EPR effect is widely used in physics, chemistry, medicine and biology as a routine method.

Unfortunately, the original setup, by means of which paramagnetic resonance signals were observed for the first time was not available. Therefore, the museum

workers had to reconstruct it by using the laboratory logbooks and Zavoisky's thesis. Now it is one of the main working exhibits, which strikes specialists by its simplicity. The setup comprises a welding transformer with a connected solenoid coil and Hartmann & Braun ammeter, an autodyne oscillator (self-oscillating unit), a low-frequency amplifier of Abbot's profile meter, and an oscillograph. The investigated sample is put into the inductance coil of the oscillator, then placed into a solenoid-generated external magnetic field. Its electrons "respond" by energy absorption only at their natural frequency. The signal thus generated is applied to the amplifier and to the oscillograph.

We should yet mention another personal feature of Zavoisky's as manifested in his mature years, when he became member of the national Academy of Sciences, namely, his passion for painting. As Zavoisky explained, he was fond of watching the light and shade of objects, their fantastic silent movements, and he liked to paint shadows cast by a table-lamp. His thirteen water-color and pastel paintings as well as drawings making up a significant part of the collection show him a man of fine fiber with a deep sense of the world's diversity.

Our museum is meant for guests with a special interest in the history of physics. It is well known to Russian and foreign experts alike. Scientists of world renown have visited it, such as the author of the semiphenomenological theory of superconductivity, Nobel Prizewinner (2003) Acad. Vitaly Ginzburg (Russia); the discoverer of superconductivity in ceramic materials, a Nobel Prizewinner (1987) and a foreign member of the Russian Academy of Sciences Karl Alex Miiller (Switzerland), a foremost authority on biological systems studied by radio-spectro-scopic methods; the Founding President of the European Electron Paramagnetic Resonance Society Klaus Möbius (Germany)... Kazan University undergraduates and postgraduates are regular visitors to the memorial laboratory. They regard Zavoisky as a fine example of an inspired and creative scientist who, in the hard wartime conditions, discovered a fundamental phenomenon of great importance for physics and all natural sciences.

In 1991 the International Zavoisky Prize was instituted in Kazan; it is awarded for signal achievements in the field of magnetic resonance by the Kazan Physics and Technology Institute, the Academy of Sciences of Tatarstan and the Springer-Verlag (Vienna-New York). By tradition, winners of the award visit our memorial laboratory. One of the entries made in the honorary visitors' book by the Zavoisky Award winner Klaus Möbius (1994), director of the Max Planck Institute for Polymer Research (Mainz, Germany) Hans Wolfgang Spiess (2010) and also by scientists of the University of North Alabama and the University of Arizona (USA) concludes with the following words: "The exhibits remind us that scientific knowledge and inspiration are the prime-movers of technologies!"

This work was supported by the RFFI grant 11-06-00251-a