Isaac B. Bersuker (Russian: Исаáк Бóрухович (Бори́сович) Берсýкер; born February 12, 1928) is a Romanian-born Soviet-Moldovan-American theoretical physicist and quantum chemist whose principal research is in chemical physics, solid-state physics, and theoretical chemistry. Known for his "life-long years of experience in theoretical chemistry" working on the electronic structure and properties of coordination compounds, Isaac B. Bersuker is "one of the most widely recognized authorities" in the theory of the Jahn–Teller effect (JTE) and the pseudo-Jahn–Teller effect (PJTE). His accomplishments include explaining the polarization of the atomic core in Rydberg atoms, the effect of tunneling splitting in molecules and solids with a strong JTE, and the discovery of the PJTE origin of ferroelectricity in cubic perovskites. For many years, known as the leading expert in JTE and PJTE, Bersuker has served as the permanent chairman of the international steering committee of the Jahn–Teller symposia. His present affiliation is with the Oden Institute for Computational Engineering and Science of the Department of Chemistry of the University of Texas at Austin. According to Google Scholar, he published 493 titles, including books, review articles, regular articles, and short communications.
Early life, education, and career Isaac (Izya) Bersuker was born on February 12, 1928, in Chișinău, then part of Greater Romania, to a low-income family of Bessarabian Jewish descent. His father Boruch Bersuker was a carpenter, and his mother Bella Bersuker (Russian: Бéлла Хáймовна Берсýкер, 1896–1981) was a housewife with five kids. As a boy in a family of a modest background, Isaac got his elementary school education in Talmud Torah and ORT. He was 13 years old when the tragic events of World War II forced his Jewish family to run from the Nazis to an Azerbaijan village. Deprived of the traditional middle and high-school education, he spent four years farming in Azerbaijan kolkhoz. After the war, native Romanian, he barely spoke Russian. Yet, in a self-education way, in а two-year term, he managed to complete a four-year high-school program in a Russian school and enrolled at Chișinău State University. A fascinating autobiographical section in describes "his scientific ascent, starting from a Jewish childhood in Bessarabia and frequently hampered by antisemitic state directives under the Stalin regime." Dedicated to the study of theoretical physics, in 1952, Bersuker graduated from the university with a master's degree in physics. He began his scientific research in atomic spectroscopy as a post-graduate student at Leningrad State University, working under Mikhail Veselov at the Division of Quantum Mechanics led by its Chair Vladimir A. Fock. Here, in 1957, Bersuker received his Candidate of Sciences degree and in 1964 his Doctor of Sciences degree. From 1964 to 1993, back in Chișinău, Bersuker continued his scientific research at the Institute of Chemistry of the Moldavian branch of the USSR Academy of Sciences. In 1964, he founded the Laboratory of Quantum Chemistry also dubbed the Chișinău school of the Jahn–Teller effect. Elected as a Corresponding Member of this academy in 1972 and a full Member in 1989, Bersuker moved to the United States. In 1993, he became a senior research scientist and professor of the department of chemistry at the University of Texas at Austin. Bersuker served as a doctoral and habilitation supervisor for 31 post-graduate students and post-docs. According to K. Alex Müller, Bersuker was and still is "in full swing at the university, writing books, discussing with great wit, and quick to understand". In the late 1980s, owing to Bersuker's high motivating role, leadership, and creative ingenuity, Bersuker's school was called "the capital of the Jahn–Teller effect" by some.
Research
Atomic spectroscopy In his Ph.D. thesis, Bersuker developed the theory of core polarization and its effect on optical transitions in Rydberg atoms. At the time, this was a puzzling problem in absorption spectroscopy. The absorption of light by alkali atoms appeared to violate the electric dipole sum rule. According to Bersuker, the solution to the problem is in the instantaneous polarization of the atomic core by the incident electromagnetic wave creating an additional perturbation to the excitation of the valence electron. Related to this problem, he worked out the adiabatic separation of motion of the valence and the atomic core electrons in electronic structure calculations of atoms. First introduced in 1957, still, decades later, Bersuker's ideas of electron polarization by the incident electromagnetic wave and of the atomic core polarization by the valence electron is used and further explored in atomic spectroscopy.
… excerpt ends here. Continue reading the full article.
