Nikolay Nikolayevich Semyonov

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Nikolay Nikolayevich Semyonov (or Semenov), (15 April 1896 – 25 September 1986) was a Russian/Soviet physicist and chemist. Semyonov was awarded the 1956 Nobel Prize in Chemistry for his work on the mechanism of chemical transformation.

Semyonov was born in Saratov, the son of Elena Dmitrieva and Nikolai Alex Semyonov. He graduated from the department of physics of Petrograd University (1913–1917), where he was a student of Abram Fyodorovich Ioffe. In 1918, he moved to Samara, where he was enlisted into Kolchak's White Army during Russian Civil War.

In 1920, he returned to Petrograd and took charge of the electron phenomena laboratory of the Petrograd Physico-Technical Institute. He also became the vice-director of the institute. During that difficult time, Semyonov, together with Pyotr Kapitsa, discovered a way to measure the magnetic field of an atomic nucleus (1922). Later the experimental setup was improved by Otto Stern and Walther Gerlach and became known as Stern–Gerlach experiment.

In 1925, Semyonov, together with Yakov Frenkel, studied kinetics of condensation and adsorption of vapors. In 1927, he studied ionisation in gases and published an important book, Chemistry of the Electron. In 1928, he, together with Vladimir Fock, created a theory of thermal disruptive discharge of dielectrics.

He lectured at the Petrograd Polytechnical Institute and was appointed Professor in 1928. In 1931, he organized the Institute of Chemical Physics of the USSR Academy of Sciences (which moved to Chernogolovka in 1943) and became its first director. In 1932, he became a full member of the Soviet Academy of Sciences.

Semyonov's outstanding work on the mechanism of chemical transformation includes an exhaustive analysis of the application of the chain theory to varied reactions (1934–1954) and, more significantly, to combustion processes. He proposed a theory of degenerate branching, which led to a better understanding of the phenomena associated with the induction periods of oxidation processes.

Semyonov wrote two important books outlining his work. Chemical Kinetics and Chain Reactions was published in 1934, with an English edition in 1935. It was the first book in the U.S.S.R. to develop a detailed theory of unbranched and branched chain reactions in chemistry. Some Problems of Chemical Kinetics and Reactivity, first published in 1954, was revised in 1958; there are also English, American, German, and Chinese editions. In 1956, he was awarded the Nobel Prize in Chemistry (together with Sir Cyril Norman Hinshelwood) for this work.

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Pyotr Leonidovich Kapitsa

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Pyotr Leonidovich Kapitsa(8 July 1894 – 8 April 1984) was a leading Soviet physicist and Nobel laureate, best known for his work in low-temperature physics.

Kapitsa was born in Kronstadt, Russian Empire to Bessarabian-Volhynian-born parents Leonid Petrovich Kapitsa, a military engineer who constructed fortifications, and Olga Ieronimovna Kapitsa from the Ukrainian noble family Stebnytski. Kapitsa's studies were interrupted by the First World War, in which he served as an ambulance driver for two years on the Polish front. He graduated from the Petrograd Polytechnical Institute in 1918. He subsequently studied in Britain, working for over ten years with Ernest Rutherford in the Cavendish Laboratory at the University of Cambridge, and founding the influential Kapitza club. He was the first director (1930–34) of the Mond Laboratory in Cambridge. In the 1920s he originated techniques for creating ultrastrong magnetic fields by injecting high current for brief periods into specially constructed air-core electromagnets. In 1928 he discovered the linear dependence of resistivity on magnetic field for various metals in very strong magnetic fields.

In 1934 Kapitsa returned to Russia to visit parents but was not allowed by Stalin's government to travel back to Great Britain.

As his equipment for high magnetic field research remained in Cambridge (although later Ernest Rutherford negotiated with British government the possibility of shipping it to the USSR), he changed the direction of his research to low temperature research, beginning with a critical analysis of the existing methods for obtaining low temperatures. In 1934 he developed new and original apparatus (based on the adiabatic principle) for making significant quantities of liquid helium.

Kapitsa formed the Institute for Physical Problems, in part using equipment which the Soviet government bought from the Mond Laboratory in Cambridge (with the assistance of Rutherford, once it was clear that Kapitsa would not be permitted to return).

In Russia, Kapitsa began a series of experiments to study liquid helium, leading to the discovery in 1937 of its superfluidity (not to be confused with superconductivity). He reported the properties of this new state of matter in a series of papers, for which he was later awarded the Nobel Prize in Physics "for basic inventions and discoveries in the area of low-temperature physics". In 1939 he developed a new method for liquefaction of air with a low-pressure cycle using a special high-efficiency expansion turbine. Consequently, during World War II he was assigned to head the Department of Oxygen Industry attached to the USSR Council of Ministers, where he developed his low-pressure expansion techniques for industrial purposes. He invented high power microwave generators (1950–1955) and discovered a new kind of continuous high pressure plasma discharge with electron temperatures over 1,000,000K.

Immediately after the war, a group of prominent Soviet scientists (including Kapitsa in particular) lobbied the government to create a new technical university, the Moscow Institute of Physics and Technology. Kapitsa taught there for many years. From 1957, he was also a member of the presidium of the Soviet Academy of Sciences.

In 1978, Kapitsa won the Nobel Prize in Physics "for his basic inventions and discoveries in the area of low-temperature physics" and was also cited for his long term role as a leader in the development of this area. He shared the prize with Arno Allan Penzias and Robert Woodrow Wilson, who won for discovering the cosmic microwave background.

Kapitsa resistance is the thermal resistance (which causes a temperature discontinuity) at the interface between liquid helium and a solid. The Kapitsa–Dirac effect is a quantum mechanical effect consisting of the diffraction of electrons by a standing wave of light. In fluid dynamics, the Kapitsa number is a dimensionless number characterizing the flow of thin films of fluid down an incline.

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Lev Davidovich Landau

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Lev Davidovich Landau (January 22, 1908 – 1 April 1968) was a Soviet physicist who made fundamental contributions to many areas of theoretical physics. His accomplishments include the independent co-discovery of the density matrix method in quantum mechanics (alongside John von Neumann), the quantum mechanical theory of diamagnetism, the theory of superfluidity, the theory of second-order phase transitions, the Ginzburg–Landau theory of superconductivity, the theory of Fermi liquid, the explanation of Landau damping in plasma physics, the Landau pole in quantum electrodynamics, the two-component theory of neutrinos, and Landau's equations for S matrix singularities. He received the 1962 Nobel Prize in Physics for his development of a mathematical theory of superfluidity that accounts for the properties of liquid helium II at a temperature below 2.17 K (−270.98 °C).

Landau was born on 22 January 1908 in Baku, Azerbaijan, in what was then the Russian Empire. Landau's father was an engineer with the local oil industry and his mother was a doctor. He learned to differentiate at age 12 and to integrate at age 13. Landau graduated in 1920 at age 13 from gymnasium. His parents considered him too young to attend university, so for a year he attended the Baku Economical Technical School. In 1922, at age 14, he matriculated at the Baku State University, studying in two departments simultaneously: the Departments of Physics and Mathematics, and the Department of Chemistry. Subsequently, he ceased studying chemistry, but remained interested in the field throughout his life.

In 1924, he moved to the main centre of Soviet physics at the time: the Physics Department of Leningrad State University. In Leningrad, he first made the acquaintance of theoretical physics and dedicated himself fully to its study, graduating in 1927. Landau subsequently enrolled for post-graduate studies at the Leningrad Institute of Physics and Technology where he eventually received a doctorate in Physical and Mathematical Sciences in 1934. Landau got his first chance to travel abroad during the period 1929–1931, on a Soviet government—People's Commissariat for Education—travelling fellowship supplemented by a Rockefeller Foundation fellowship. By that time he was fluent in German and French and could communicate in English. He later improved his English and learned Danish.

After brief stays in Göttingen and Leipzig, he went to Copenhagen on 8 April 1930 to work at the Niels Bohr's Institute for Theoretical Physics. He stayed there till 3 May of the same year. After the visit, Landau always considered himself a pupil of Niels Bohr and Landau's approach to physics was greatly influenced by Bohr. After his stay in Copenhagen, he visited Cambridge (mid-1930), where he worked with P. A. M. Dirac, Copenhagen (20 to 22 September – 22 November 1930), and Zurich (December 1930 to January 1931), where he worked with Wolfgang Pauli. From Zurich Landau went back to Copenhagen for the third time and stayed there from 25 February till 19 March 1931 before returning to Leningrad the same year.

Between 1932 and 1937 he headed the Department of Theoretical Physics at the National Scientific Center Kharkov Institute of Physics and Technology and lectured at the University of Kharkov and the Kharkov Polytechnical Institute. Apart from his theoretical accomplishments, Landau was the principal founder of a great tradition of theoretical physics in Kharkov, Soviet Union, sometimes referred to as the "Landau school". In Kharkov, he and his friend and former student, Evgeny Lifshitz, began writing the Course of Theoretical Physics, ten volumes that together span the whole of the subject and are still widely used as graduate-level physics texts.

Landau developed a famous comprehensive exam called the "Theoretical Minimum" which students were expected to pass before admission to the school. The exam covered all aspects of theoretical physics, and between 1934 and 1961 only 43 candidates passed, but those who did later became quite notable theoretical physicists.

Landau was the head of the Theoretical Division at the Institute for Physical Problems from 1937 until 1962. Landau led a team of mathematicians supporting Soviet atomic and hydrogen bomb development. Landau calculated the dynamics of the first Soviet thermonuclear bomb, including predicting the yield. For this work he received the Stalin Prize in 1949 and 1953, and was awarded the title "Hero of Socialist Labour" in 1954.

His students included Lev Pitaevskii, Alexei Abrikosov, Evgeny Lifshitz, Lev Gor'kov, Isaak Khalatnikov, Roald Sagdeev and Isaak Pomeranchuk.

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Germain Henri Hess

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Germain Henri Hess (7 August 1802 – 30 November 1850) was a Swiss-Russian chemist and doctor who formulated Hess's law, an early principle of thermochemistry.

Hess was born on 26 July (7 August) in Geneva, Switzerland. His father was an artist and in 1805 moved the family to Russia to work as a tutor to a rich family. His Swiss-born mother was tutor as well and Hess had the benefit of learning German and French at home. In 1817, his family moved to Derpt, Russian Empire (now Tartu, Estonia), where he went to a private school for two years, and then to Derpt Gymnasium, which he finished in 1822. In autumn of the same year Hess studied medicine at the University of Derpt. During that time, Chemistry department was responsible for Chemistry courses of Medicine and Pharmacy departments and Professor Gottfried W. Osann was giving the lectures which carried in German (an obvious advance for Hess). Under Osann’s supervision, Hess made chemical analyses, but also had an interest in the lectures of Professor of Physics Georges-Frédéric Parrot and Professor of Mineralogy Moritz von Engelhardt. Hess graduated with honors from Derpt University receiving a doctor of medicine degree with his dissertation entitled Something about Curative Waters, Especially Those in Russia. He qualified as a physician in 1825. By application of Professors Osann and Engelhardt, Hess was sent to Sweden, to visit Swedish chemist Jöns Jakob Berzelius and after a meeting with turned once and for all to chemistry. On his return to Russia, Hess joined an expedition to study the geology of the Urals before was appointed a doctor at Irkutsk which, according to the regulations of that time, owe to practice at a Russian frontier after having graduated. Here went to Irkutsk in August 1826.

In 1830, Hess took up chemistry full-time, researching and teaching, and later became an adjunct professor of Chemistry at the St. Petersburg Academy of Sciences. His most famous paper, outlining his law on thermochemistry, was published there in 1840. His principle, a progenitor for the first law of thermodynamics, came to be called Hess's law. It states that in a series of chemical reactions, the total energy gained or lost depends only on the initial and final states, regardless of the number or path of the steps. This is also known as the law of constant heat summation.

Like most of his colleagues, Hess was primarily an experimental chemist interested in the discovery and analysis of new substances. However, he also developed a strong interest for theoretical investigations. In particular, he wondered how chemical affinity relates to heat in chemical reactions. His experiments on various hydrates of sulfuric acid showed that the heat released when they formed was always the same, whether the reactions proceeded directly or through intermediates (1840). Hess thus formulated a special case of the conservation of energy two years before Julius Robert von Mayer stated a more general principle, in 1842. Hess was fully aware of the importance of his own contribution.

In 1842, Hess proposed the law of thermoneutrality, which states that no heat is evolved in the exchange reactions of neutral salts in aqueous solution. A full explanation would only be given 45 years later, in terms of electrolytic dissociation, by the Swedish chemist Svante Arrhenius.

After these two major discoveries, Hess was influential in the development of chemistry in Russia. His book Osnovania Chistoy Khimii (Fundamentals of Pure Chemistry) went through seven editions and remained the standard Russian textbook for undergraduate chemistry until 1861. Hess was active as a teacher and mentor of young scientists, until his poor health forced him to retire, in 1848.

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