Vadim Aleksandrovich Atsarkin
June, 13. 2006 is the 70 th anniversary of Vadim Aleksandrovich Azarkin, Editor of MRSej, Doctor of Science (in physics and mathematics), Professor, talented scientist whose name is world-wide known in Radiospectroscopy. His contribution to the development of the spin thermodynamics in solid electron and nuclear paramagnets turned to be fundamental.
(to 70 th anniversary)
Vadim A. Atsarkin graduated with excellent diploma from the Semiconductor Physics Department of the Moscow State University ; however, his scientific research activities started in Quantum Electronics Laboratory headed by Doctor of Science, Prof. M.E. Zhabotinskii in the Radio Engineering and Electronics Institute of the Academy of Sciences of USSR . Initially, he searched and investigated materials for masers with improved parameters, i.e., recently discovered and put into foundation of Quantum Radio Engineering and Electronics supersensitive quantum amplifiers. The investigation method was Electronic Paramagnetic Resonance (EPR) discovered by Ye.K. Zavoiskii in 1944 in Kazan . This method made it possible to investigate efficiently various phenomena related to resonance absorption of radio waves by electron and nuclear paramagnets, which became a basis of masers' construction. In a domain yet unknown for him, V.A. Atsarkin quickly achieved a significant progress, successfully defended his candidate of science thesis, and started research in the spin thermodynamics in solid electron and nuclear paramagnets, that came into being during 60s and 70s of 20 th Century. By that time, B.N. Provotorov already created a two-temperature theory of magnetic resonance which introduced into Physics the concept of a dipole order characterizing mutual orientations of spins in each other local fields, its experimental confirmation was obtained in NMR. However, some specialists were skeptical with respect to applicability in EPR of this two-temperature theory due to a chaotic distribution of paramagnetic impurities in magnetically diluted paramagnetic crystals and an inhomogeneous broadening of EPR lines. M.I. Rodak, a colleague of V.A. Atsarkin by the laboratory, proved that the two-temperature theory leads to a new effect, i.e., an induced irradiation under saturation on the wing of resonance line of spin system. A series of original experiments carried out by V.A. Atsarkin confirmed this prediction and turned in a “touchstone” for verifying the applicability of the two-temperature theory to EPR.
In further investigations V.A. Atsarkin along with colleagues discovered a direct heat contact between the electron dipole-dipole subsystem and the nuclear Zeeman subsystem, which generated the relaxation of nuclei via an electron dipole reservoir and now is serving as one of the basic mechanisms of Dynamic Nuclear Polarization (DNP). The cross-relaxation method of DNP, which is realized under cross-relaxation between EPR lines and does not require a saturation of forbidden electron-nuclear transitions, was also discovered at the same time. These outstanding results were put into foundation of his doctor of science thesis defended in 1971; later, in 1988, these results were recognized as a discovery. V.A. Atsarkin generalized an extensive cycle of works dedicated to DNP problems actual in those years in his monograph “Dynamic Nuclear Polarization in Solid Dielectrics” (Moscow, “Nauka” Publishers, 1980) which up to now serves as one of fundamental handbooks in this field.
In 1973, V.A. Atsarkin predicted and proved together with O.A. Ryabushkin the effect of enhanced longitudinal susceptibility. The longitudinal susceptibility was measured first by Gorter as far back as in 30s; however, this important technique had a limited application in view of its low sensitivity. V.A. Atsarkin suggested that investigations should be carried out in the conditions of ERP line's saturation providing strong cooling of the electron dipole reservoir; this enhances the sensitivity by several orders (“Atsarkin effect”). The posterior development of this method by V.A. Atsarkin and his colleagues led to the direct observation of Nuclear Magnetic Resonance (NMR) in rotating coordinate systems. Under these conditions, a strong narrowing of NMR line is possible with which ordinary two-particle dipole-dipole interactions of nuclei disappear and the main role passes to significantly more weak multispin interactions, while the relaxation measurements can be carried out in small effective fields. This led to the development of a new method for detecting slow (at velocities 10 2 – 10 4 ? -1 ) molecular movements (V.A. Atsarkin, T.N. Khazanovich, A.Ye. Mefed).
The new methods developed for ERP spectroscopy were successfully applied by V.A. Atsarkin and his colleagues to solving important problems of Solid State Physics, e.g., the question of the shape of hole burned out in dipole EPR spectrum, the investigation of regularities of spectral transition in non-ordered paramagnets, direct measurement of the time of spin-lattice relaxation of paramagnetic centers in High-Temperature Superconductors, the analysis of metal-dielectric translation in fullerids, the dipole broadening and exchange narrowing of EPR lines of paramagnetic centers on the solid body surface and concentration dependences of EPR spectra in manganites.
The outstanding scientific results, encyclopedic knowledge, professionalism, wide scope of interests, benevolence and readiness to discuss scientific problems with any person asking for help – all these virtues conciliated a universal respect to V.A. Atsarkin. He is member of Program Committees of many conferences and scientific schools on Magnetic Resonance and he is always in the focus of discussions on new scientific problems. On conferences, this is a rule to observe “live queues” of theorists and experimentalists desiring to discuss with V.A. Atsarkin a wide set of questions from various fields of Magnetic Resonance's physics' problems. Being a professional experimentalist, V.A. Atsarkin at the same time deeply knows the theory of phenomena under investigation. An evidence to this virtue was provided by a theoretical article concerning quasi-equilibrium stabilization in spin system of solid paramagnet (1985), where he constructed a clear physical picture of the process and gave an adequate mathematical apparatus, and thus solved long disputes among some theorists. A monthly All-Russia seminar on Magnetic Resonance under his supervision, known also as “Atsarkin' Seminar”, works already more than 25 years in the Radio Engineering and Electronics Institute of the RAS. The characteristic style of this seminar is a detailed discussion with a reporter of the theme of his/her report before its placement into agenda and always bright, benevolent concluding words with the deep analysis of the reported work. This seminar became a real scientific school for many future candidates and doctors of science.
The colleagues, disciples, and friends of Vadim A. Atsarkin use this way to congratulate him with this significant date and wish strong health and new creative successes in all fields.
V.V. Demidov, F.S. Dzheparov, E.B. Feldman, N.P. Fokina, B.I. Kochelayev, T.N. Khazanovich, Ye.K. Khenner, A.A. Lundin, A.Ye. Mefed, N.Ye. Noginova, M.I. Rodak, O.A. Ryabushkin, K.M. Salikhov, M.S. Tagirov, V.A. Zhikharev, V.Ye. Zobov.