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Research Areas and Major Contributions
• Field of Specialization: chemical physics, physical chemistry, quantum chemistry, theoretical chemistry, solid-state physics, materials science
• Outstanding contributions:
In atomic spectroscopy, Bersuker developed the theory of core polarization and its effect on optical transitions in Rydberg atoms. According to Bersuker, the solution to the problem is the instantaneous polarization of the atomic core by the incident electromagnetic wave, which creates an additional perturbation to the excitation of the valence electron. Related to this problem, he worked out the adiabatic separation of motions of the valence and the atomic core electrons in electronic structure calculations of atoms.
Bersuker's contributions to the theory of the Jahn-Teller effect and pseudo-effect with applications to physical and chemical phenomena are reflected in his monographs and major reviews on this subject. First published in 1961–1962, his contributions to the theory of the Jahn-Teller effect predicted the tunneling splitting of the vibronic energy levels of the systems with the Jahn-Teller effect later confirmed experimentally. In addition, Bersuker is known for revealing the significance of the pseudo-Jahn-Teller effects and showing that it may occur at any energy gaps between entangled electronic states. Most importantly, he proved that the Jahn-Teller effect and pseudo-effect are the only sources of structural instability and spontaneous symmetry breaking in polyatomic systems. They may take place in the excited states of the system. Still, when strong enough, the excited Jahn-Teller states can cross the ground state of the high-symmetry configuration and form an additional, coexisting equilibrium state with lower symmetry. The latter may also have a different spin state, leading to an interesting phenomenon of spin-crossover and magnetic-dielectric bistability.
In solid-state physics, Bersuker applied the theory of the pseudo-Jahn-Teller effect to explain the origin of ferroelectricity in perovskite-type crystals, resulting in a trend in the studies of local and cooperative properties in crystals. Because the pseudo-Jahn-Teller effect does not entangle states with different spin multiplicity, Bersuker deduced conditions and predicted possible multiferroics in some cubic perovskites.
There is quite a list of other theoretical chemistry, chemical physics, and quantum chemistry fields with a remarkable contribution from Bersuker. Bersuker introduced and developed theoretical models of vibronic mechanisms in redox properties, electron-conformational effects, chemical reactivity, and catalysis in his seminal papers. He is known for revealing the role of the Jahn-Teller effects and pseudo-effects in the properties of mixed-valence compounds. In addition, he discovered the effect of coordination covalent bonding and the role of the Jahn-Teller effect in the so-called "plasticity effect". Also, Bersuker worked out the method of a quantum-mechanics/molecular-mechanics approach to electronic structure calculations of large organometallic systems when there is a charge transfer between the QM and the MM parts. The name Bersuker is associated with the semiempirical approach to relativistic electronic structure calculations and a method of estimating molecular-orbital parameters from Mössbauer spectra. He created and applied the electron-conformational method to computer-aided drug design and toxicology in another series of publications. This methodology revealed the chemical origin of odorant activity, including the source of musk odor.
Recognition and awards
• In 1976, The phenomenon of tunneling splitting of energy levels of polyatomic systems with electronic degeneracy was qualified as a scientific discovery and registered in the State Register of the USSR (Diploma No. 202).
• Owing to Bersuker's highly motivating role, leadership, and creative ingenuity, Bersuker's school was called "the capital of the Jahn–Teller effect."
• Evaluated by AI ScholarGPS by his scientific achievements, Bersuker was assessed as belonging to 0.5% of TOP SCHOLAR Worldwide.
• For about 20 years, known as the leading expert in Jahn-Teller effects and pseudo-effects, Bersuker was the permanent chairman of the international steering committee of the Jahn–Teller symposia.
• Owing to Bersuker's highly motivating role, leadership, and creative ingenuity, Chișinău school was called "the capital of the Jahn–Teller effect."
• Moldavian SSR State Prize in Science and Technology (1979)
• Order of Honour (Moldova) (2004)
• The Medal "Scientific Merit I class" (Moldova) (2021)
Publications and scientific papers
• Isaac Bersuker published more than 440 peer-reviewed papers in international scientific journals, including 40 major reviews and 16 science books. Google Search for Isaac Bersuker offers more than 1,2 million returns.
• Among his most important books, six were written on the Electronic Structure of Coordination Compounds (4 in Russian and 2 in English), and six on the Jahn-Teller Effect (2 in Russian and 4 in English). One monograph was written in 1962 in collaboration with A. V. Ablov, two books in 1983 and 1989 were written with V. Polinger, one book in 1984 was written with a larger group of co-authors, and the other eight were written solo.
• Two more of Bersuker's monographs are in preparation and will be published this year. One, Electronic Structure and Properties of Transition Metal Compounds was written in collaboration with his former student from China, Yang Liu. It is ready for publication this Fall by Wiley, the American academic publisher. The second book, The Jahn-Teller Effects and Pseudo-Effects with V. Polinger, will be published by Springer Verlag in Germany.
• Scientists, teachers, and students use Bersuker's books and academic papers with or without citations (citations in Russian journals and books before 1993 are not available); direct citations: 12,320. Many publications are used as online reading. Here are two examples: (a) I.B. Bersuker:, The Pseudo Jahn-Teller Effect – a Two-State Paradigm in Formation, Deformation, and Transformation of Molecular Systems and Solids, Chemical Reviews, 113, 1351-1390 (2013); DOI: 10.1021/cr300279n. According to Google Scholar, it has 10,226 views. (b) Bersuker I. B., Jahn–Teller and Pseudo-Jahn–Teller Effects: From Particular Features to General Tools in Exploring Molecular and Solid State Properties. Chem. Rev. 2021, 121, 3, 1463-1512; https://dx.doi.org/10.1021/acs.chemrev.0c00718. According to Google Scholar, it has 6,141 views.
Memorable Quotes
• The most important decision I made in 1945, at seventeen when our family returned to Chișinău from evacuation - was to continue studying and devote myself to scientific research. This decision determined my entire life path and the fate of my later children and grandchildren, my students and pupils.
• Scientific recognition is achieved by those who not only put forward new ideas but also have a strong character and can defend their ideas when everyone dismisses them and does not take them seriously.
Scientific legacy
Bersuker's academic publications have a high impact on the scientific community. According to Google Scholar, since 1993, when he moved to the United States, Bersuker's articles and books have been cited more than 12 thousand times; his h-index is 41, and his i10 index is 141. Isaac B. Bersuker has supervised doctoral and habilitation theses for 31 graduate and postdoctoral students.
Contact
• Email address: [email protected]
• ORCiD: https://orcid.org/0000-0002-6382-7721
• Scopus
• WikipediA (Romanian)
• WikipediA (English)
• WikipediA (German)
• WikipediA (Russian)
• Academia
• ResearchGate
• Math-Net.Ru
• Laboratory of Physical and Quantum Chemistry
• Google Scholar
Comments/Tributes
• Müller, K. Alex (2003). "Encounters with Isaac Bersuker". In Ceulemans, Arnout; et al. (eds.). Advances in Quantum Chemistry. Manifestations of Vibronic Coupling in Chemistry and Physics. Vol. 44. San Diego, CA: Elsevier Science. pp. xxxv–xxxvi. ISBN 0-12-034844-6.
• Borshch, S.; Polinger, V. (2003) "Anniversary Isaac Bersuker 75". In Ceulemans, Arnout; et al. (eds.). Advances in Quantum Chemistry. Manifestations of Vibronic Coupling in Chemistry and Physics. Vol. 44. San Diego, CA: Elsevier Science. pp. xxxiii–xxxv. ISBN 0-12-034844-6.
• Boggs, James E.; Polinger, Victor Z., eds. (2008). The Jahn–Teller Effect and Beyond. Selected works of Isaac Bersuker with Commentaries. Chișinău, Moldova: The Acad. of Sciences of Moldova and The University of Texas at Austin (published December 17, 2008). pp. 10–31. ISBN 978-9975-62-212-7.
• Tsukerblat, B.; Sister, Yu.; Zhignea, K., (2014) "Academician Isaac Borisovich Bersuker”, The House of Scientists and Experts of Rechovot, http://rehes.org/rus_iud/tom12-bersuker.html
Importance for science and development
Acad. I. Bersuker is a distinguished figure in theoretical and computational chemistry, whose contributions have had a significant impact on the understanding of fundamental molecular phenomena. His work on the Jahn-Teller effect and vibronics has profoundly influenced the development of modern science, opening new perspectives in chemistry, physics, and advanced materials. Through his innovative research and international collaborations, acad. Bersuker has contributed to the education of a new generation of scientists and the continuous progress of science in the 21st century.
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