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Cherenkov, Pavel A.

( Russian physicist, Nobel Prize in Physics, 1958)

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Biography Cherenkov, Pavel A.
Russian physicist Pavel Cherenkov was born in New Chigle near Voronezh. His parents, Aleksei and Mariya Cerenkov were peasants. After graduating in 1928. Physics and Mathematics, Voronezh University, he worked for two years a teacher. In 1930. He became a graduate student at the Institute of Physics and Mathematics of the USSR in Leningrad, and received his Ph.D. in 1935. Then he became a Fellow of the Institute of Physics. P.N. Lebedev in Moscow, where he worked in the future.
In 1932, Mr.. under the guidance of Academician SI. Vavilov V. began to explore the light arising in the solution absorption of high energy radiation, such as emission of radioactive substances. He was able to show that in almost all cases, the light gave rise to certain causes, such as fluorescence. When the fluorescence of the incident energy excites the atoms or molecules to higher energy states (according to quantum mechanics, . Each atom or molecule has a characteristic set of discrete energy levels), . from which they quickly returned to lower energy levels,
. The difference between the energies of higher and lower states is allocated as a unit of radiation - quantum, whose frequency is proportional to the energy. If the frequency belongs to the visible region, the radiation manifests itself as light. Since the difference between the energy levels of atoms or molecules, . through which the substance is excited, . Returning to the lowest energy state (ground state), . usually differ from the quantum energy of the incident radiation, . emission from the absorbing material has a different frequency, . than generating its radiation,
. Typically, these frequencies are below.
However, H. found that gamma-rays (which have much more energy and hence frequency than X-rays) emitted by radium, give a weak blue luminescence in the liquid, which is not found a satisfactory explanation. This glow observed and other. For dozens of years before the V. he saw Maria and Pierre Curie, studying radioactivity, but it was thought that this is just one of many manifestations of luminescence. CH. acted in a very methodical. He enjoyed double-distilled water to remove all impurities that may be hidden sources of fluorescence. He applied the heat and add chemicals such as potassium iodide and silver nitrate, which reduces the brightness and other characteristics have changed conventional fluorescence always traveling the same experiments with the control solutions. Light in the control solution changes, as usual, but the blue glow remained unchanged.
Study greatly complicated by the fact that H. no high-energy radiation sources and sensitive detectors, which later became the most common equipment. Instead, he had to use the weak natural radioactive materials for gamma-rays, . which gave a barely noticeable blue glow, . instead of the detector to rely on their own vision, . sharpening with the help of a long stay in the dark,
. Nevertheless, he managed to convincingly show that the blue glow is something extraordinary.
Significant discovery was unusual polarization luminescence. Light is the periodic oscillations of the electric and magnetic fields, whose intensity increases and decreases in magnitude and change direction in the plane perpendicular to the direction of motion. If the directions of the fields are limited by special lines in this plane, as in the case of reflection from the plane, then we say that the light is polarized, but polarization is nevertheless perpendicular to the direction of propagation. In particular, if the polarization occurs when the fluorescence, the light emitted from an excited substance is polarized at right angles to the incident beam. CH. found that the blue luminescence polarized parallel and not perpendicular to the direction of incident gamma rays. Studies conducted in 1936, also showed that the blue glow is not emitted in all directions, and extends forward of the incident gamma rays and forms a light cone whose axis coincides with the trajectory of the gamma-rays. This was the key to his colleagues, Ilya Frank and Igor Tamm, who created a theory which gave a full explanation of the blue glow, now known as Cherenkov radiation (Vavilov - Cherenkov radiation in the Soviet Union).
. According to this theory, photons absorbed by an electron in the liquid, causing it to burst from the parent atom
. This collision has been described by Arthur X. Compton and is called the Compton effect. The mathematical description of this effect is very similar to the description of collisions of billiard balls. If the exciting beam has a sufficiently high energy, knocked the electron flies at high speed. A remarkable idea of Frank and Tamm was the fact that the Cerenkov radiation occurs when the electron moves faster than light. Others, apparently withheld from such assumptions fundamental postulate of relativity, Albert Einstein, according to which the particle velocity can not exceed the speed of light. However, this limitation is relative and valid only for the speed of light in vacuum. In substances such as liquids or glass, light travels at a slower rate. In liquids, electrons knocked out of atoms can move faster than light if the incident gamma-rays have sufficient energy.
. Cone Cherenkov radiation is analogous to waves generated by the motion of the boat at a speed exceeding the speed of wave propagation in water
. It is also similar to the shock wave that appears when you move the sound barrier.
For this work, H. received his doctorate in physics and mathematics in 1940. Together with Vavilov, Tamm and Frank, he was awarded the Stalin (later changed to the State) Award of the USSR in 1946
In 1958, Mr.. with Tamm and Frank H. was awarded the Nobel Prize in Physics "for the discovery and interpretation of the Cherenkov effect '. Manne Siegbahn from the Royal Swedish Academy of Sciences noted in his speech, . that 'the discovery of, . now known as the Cerenkov effect, . an interesting example of, . as a relatively simple physical observation with the right approach can lead to important discoveries and to pave new paths for further research '.,
. Commenting on the awarding of the first Soviet scientists the Nobel Prize in Physics, . newspaper 'The New York Times' noted, . it shows' truly international recognition of high quality experimental and theoretical research in physics, . held in the Soviet Union ',
. Such recognition was of the ironic nature (at least in part) because during the original investigations of H. his primitive methods of doing for many physicists questionable findings.
Over the years, the theory of Cerenkov radiation, while maintaining the fundamental importance, had no practical applications. Subsequently, however, were created Cerenkov counters (based on the detection of Cerenkov radiation) to measure the rate of single high-speed particles, such as those that occur in accelerators or in cosmic rays. Determination of the rate based on the fact that the faster moving particle, the narrower becomes the Cherenkov cone. Because the Cerenkov radiation has an energy threshold and is a short pulses, with the Cerenkov counter can filter out particles with low velocities and to distinguish between two particles arriving almost simultaneously. When registering radiation is also released information about the mass and energy of the particle. This type of detector used at the opening of the antiproton (negative hydrogen nuclei), Owen Chamberlain and Emilio Segre in 1955, later it was used in the counter of cosmic rays on the Soviet artificial satellite Sputnik-111 '.
. For many years, H
. was chief of department of the Institute of. Lebedeva, after the war he began to study cosmic rays and participated in the creation of electron accelerators. For participation in the development and establishment of the Institute of. Lebedeva synchrotron he was awarded the second Stalin (State) Award in 1951. In 1959, Mr.. CH. became the head of the institute photomeson laboratory processes, where he conducted research on the photodecomposition of helium and other light nuclei and sub-atomic particles photoproducts.
. In addition to research activities, Ch, since 1944, many years he taught physics at the Moscow Energy Institute, and later at the Moscow Engineering Physics Institute
. He became a professor of physics in 1953
In 1930. CH. Putintseva married Mary, daughter of a professor of Russian Literature. They had two children.
Cherenkov was elected a corresponding member of the USSR in 1964. and academician in 1970. He three times winner of the USSR State Prize, had two Orders of Lenin, two Orders of Red Banner of Labor and other state awards

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