the field of atomic physics, one of the creators of the modern theory of atomic collisions, Honored Scientist of Russia, Professor Emeritus at St. Petersburg University, died on 15 November 2010. Yu N Demkov was born on 12 April 1926 in Leningrad into the family of engineer-architects designing many public buildings in Leningrad and other cities in the USSR. He graduated magna cum laude from high school in 1942 in the city of Yaroslavl' during the evacuation and entered the Moscow Institute of Steel in 1943. In 1944, when he was 18 years old, Y N Demkov was drafted into the acting army and served as a soldier in the First Ukrainian Front during World War II. In September 1945 he was demobilized, went back to Leningrad, and joined the sophomore class of the Department of Physics at Leningrad State University, where he worked all his life. After graduating with summa cum laude from Leningrad State University in 1949, YuNDemkov joined as an assistant the Chair of Theoretical Physics headed at that time by Academician V A Fock. His graduation thesis, ``Charge exchange in atomic collisions'', proved to be quite relevant and determined the main direction of his research for many years. Yurii Nikolaevich's PhD thesis was devoted to the variation principles in collision theory, which were closely related to the investigations of V A Fock. He defended a PhD thesis in 1954 and later wrote amonograph on the same topic, which was then translated into English and received a university prize in 1962. Yu N Demkov defended his doctoral dissertation, ``Slow collisions of atoms and molecules'', in 1967 and became a full professor in 1970. Yurii Nikolaevich worked successively as an assistant, senior researcher, associate professor, head of the laboratory of the theory of atomic collisions, and professor. From 1975 to 1991, he was the head of the Chair of QuantumMechanics. The work of Yu N Demkov on the collision theory of atoms and ions brought him scientific authority in theoretical physics in our country and later worldwide prominence. He obtained pioneering results in the theories of charge exchange, electron detachment, and other processes. The concepts of the `Demkov model' and `Demkov coupling' are well known in modern atomic physics. The second set of results obtained by Yu N Demkov concerns the problems of symmetry in atomic physics, in particular, when applied to the Fock symmetry of the hydrogen atom and harmonic oscillator. The most important among these results was the explanation of the internal symmetry of the Mendeleev Periodic Table and the so-called (n‡ l, n) energy-level occupation rule. Here, he managed to combine in whole the work of Maxwell on the so-called `fish eye', of Mendeleev, Bohr, and Fock on the hydrogen atom symmetry. Yurii Nikolaevich also obtained, together with G F Drukarev and V N Ostrovskii, fundamental results in the development of the method of zero-radius potentials in atomic physics. The results of these studies are presented in the monograph Method of Zero-Radius Potentials by Yu N Demkov and V N Ostrovskii [(Leningrad: Leningrad State University, 1975), which was translated into English (Plenum Press, 1988)] and awarded a University First-Class Prize. Yu N Demkov's significant achievement was the discovery of a new class of problems in collision theory, so-called harmonic scattering, and the development (together with I V Komarov, A P Shcherbakov, and D I Abramov) of the original theory of this scattering using conformal mappings. This work was awarded an Academician V A Fock Prize of the Russian Academy of Sciences. Other work of Demkov includes original and unexpected results obtained in neutrino focusing studies; polynomial solutions of the problem of the Uspekhi Fizicheskikh Nauk 181 (5) 565 ± 566 (2011) DOI: 10.3367/UFNr.0181.201105l.0565 Translated by M N Sapozhnikov PERSONALIA PACS number: 01.60.+q