Semenov NikolayNikolaevich

April 15, 1896, Mr.. - September 25, 1986
Russian physical chemist Nikolay Semenov was born in Saratov, in the family of Nicholas and Helena Dmitriyevna Semyonovykh. After graduating in 1913. secondary school in Samara, he joined the Physics and Mathematics Department of St. Petersburg (Leningrad) University, where, doing the famous Russian physicist Abram Ioffe, proved to be an active student.
. After graduating from university in 1917, the year of accomplishment of the Russian Revolution, C
. worked as an assistant at the Physics Department of Tomsk University in Siberia. In 1920, Mr.. On the invitation of the Ioffe. returned to Leningrad and became deputy director of the Petrograd (Leningrad) Physical-Technical Institute and head of his laboratory electronic phenomena. In collaboration with Peter Kapitza C. proposed a method of measuring the magnetic moment of an atom in an inhomogeneous magnetic field, describing an experimental process, in an article that was published in 1922. This method was later successfully developed by Otto Stern and Walther Gerlach.
The problem of ionization of gases was apparently the first scientific problem, which is interested in P. While still a university student, he published his first article, which talked about the collisions between electrons and molecules. Upon returning from Tomsk C. engaged in more research processes of dissociation and recombination in t.ch. ionization potential of metals and vapors of salt. The results of these studies and others collected in the book 'Chemistry of the electron', which he wrote in 1927. co-authored with two of his students. S. also interested in the molecular aspects of the phenomena of adsorption and condensation of vapors on a solid surface. His investigations revealed the relationship between the density of vapor and surface temperature of condensation. In 1925, Mr.. with the known theoretical physicist Yakov Frenkel, he developed a comprehensive theory of these phenomena.
Another area of interest with. at that time belonged to the study of electric fields and phenomena associated with the passage of electric current through gases and solids. The scientist, in particular, studied the passage of electric current through gases, as well as the mechanism of breakdown of solid dielectrics (electrically inert substances) under the action of electric current. Based on this recent study with. and Vladimir Fock, famed for his work in the field of quantum physics, developed a theory of thermal breakdown of dielectrics. This in turn prompted with. for the work that led to his first important contribution to the science of combustion - the creation of the theory of thermal explosion and combustion of gas mixtures. According to this theory, . warm, . released during a chemical reaction, . under certain conditions, no time to play from the reaction zone and raises the temperature of the reactants, . accelerating the reaction and leads to the separation of larger amount of heat,
. If the increase in the amount of heat is quite fast, the reaction may result in explosion.
Shortly after the end of this work in 1928. S. was appointed professor of the Leningrad Physical-Technical Institute, where he helped organize the physical-mechanical department, and also introduced teaching of Physical Chemistry. At his insistence, and with the help of his colleagues who are interested in the development of Physical Chemistry, Laboratory of Physics of the electron into a 1931. the Institute of Chemical Physics, Academy of Sciences of the USSR, and C. became its first director. In 1929, Mr.. He was elected a corresponding member of Academy of Sciences of the USSR, and in 1932. became an academician.
By this time, C. conducted in-depth studies of chain reactions. They represent a series of samoinitsiiruemyh stages in the chemical reaction, which, once begun, continues until, until you passed the last stage. Despite the fact that the German chemist Max Bodenstein first suggested the possibility of such reactions as early as 1913, the theory that explains the stages of the chain reaction and showing its speed, there was no. The key is a chain reaction is the initial stage of formation of free radicals - atoms or groups of atoms with a free (unpaired) electron and therefore highly reactive. Once formed, it interacts with the molecule in such a way that as one of the reaction products formed a new free radical. The newly-formed free radicals can then interact with another molecule, and the reaction continues as long as something did not prevent free radicals to form a similar, ie. There will not break the chain.
Particularly important is the reaction of a chain reaction of a branched chain, opened in 1923. physicists GA. Kramers and IA. Kristiansen. In this reaction, free radicals not only regenerate the active centers, but also actively multiplying, creating new circuit and forcing the reaction to go faster and faster. The actual course of the reaction depends on a number of external constraints, such as the size of the vessel in which it occurs. If the number of free radicals increases rapidly, the reaction may lead to an explosion. In 1926, Mr.. two students with. first observed this phenomenon, studying the oxidation of phosphorus vapor with water vapor. This reaction was not as it should go in line with the theories of chemical kinetics of the time. S. saw the reason for this discrepancy is that they were dealing with the result of a branched chain reaction. But this explanation was rejected by Max Bodenstein, while a recognized authority on chemical kinetics. Another two years went on an intensive study of this phenomenon with. and Cyril H. Hinshelwood, who conducted his research in England, regardless of MS, and after this period it became obvious that C. was right.
In 1934, Mr.. S. published a monograph "Chemical kinetics and chain reactions', which showed that many chemical reactions, including polymerization reactions are carried out through the mechanism of chain or branched chain reaction. In the next decade. and other scholars have accepted his theory, continued to work on clarifying the details of the chain reaction, analyzing the relative experimental data, many of which were gathered his students and staff. Later, in 1954, published his book 'On Some Problems of Chemical Kinetics and Reactivity', in which the scientist summarized the results of the discoveries made by him during the years of work on his theory.
In 1956, Mr.. S. with Hinshelwood was awarded the Nobel Prize in Chemistry 'for research in the field of mechanism of chemical reactions'. In his Nobel lecture with. an overview of their work on chain reactions: 'The theory of chain reaction opens the possibility to get closer to solving the main problems of theoretical chemistry - the relationship between reactivity and structure of particles entering the reaction ... It is hardly possible in any degree was to enrich the chemical technology or even to achieve a decisive victory in biology without the knowledge ... Need to combine the efforts of educated people of all countries and to solve this most important issue in order to uncover the secrets of chemical and biological processes for the benefit of peaceful development and prosperity of mankind '.
Once in 1944. S. was appointed Professor of MSU, he continued to publish their work on various issues up to the 80-ies. Its volume work on the oxidation of vapors of phosphorus has not lost its relevance even today, 50 years from the date of its creation. During the Second World War, Institute of Chemical Physics, he moved to Moscow. Many of the studies being carried out there are directly related to the initial scientific interests AS, although today they are carried out using mass spectrometry and quantum mechanics.
. Even in his later years St., according to his colleagues, remained enthusiastic about science, creative personality, which featured overflowing energy
. He was tall and lean, he loved to hunt and work in the garden, was fond of architecture. S. and Natalia Burtseva, whom he married in 1924, lived in Moscow, where she taught singing. In the couple had two children: son and daughter. S. died September 25, 1986, Mr.. the age of 90 years.
For work on the development of the theory of chain reactions. in 1941. was awarded the Soviet government awards - the Stalin Prize. Among his other awards - the Order of Lenin, Order of Red Banner of Labor, the Gold Medal Lomonosov Academy of Sciences. Holder of honorary degrees from several European universities, with. was elected an honorary member of the Royal Society of London. USSR Academy of Sciences scientist held a large number of official posts. In addition, he was elected a member of the academies of many other countries including the United States.