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.
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.
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.
[4] A fascinating autobiographical section in [5] describes "his scientific ascent, starting from a Jewish childhood in Bessarabia and frequently hampered by antisemitic state directives under the Stalin regime.
He began his scientific research in atomic spectroscopy as a post-graduate student at Leningrad State University, working under Mikhail G. Veselov[7] at the Division of Quantum Mechanics[8] led by its Chair Vladimir A. Fock.
From 1964 to 1993, back in Chișinău, Bersuker continued his scientific research at the Institute of Chemistry[9] of the Moldavian branch of the USSR Academy of Sciences.
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 ‒ as I had known him for well over thirty years.
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.
[18] Bersuker's contributions to the JTE and PJTE theory with applications to physical and chemical phenomena are reflected in his several monographs (some of them written and published with the assistance and involvement of other authors) and major reviews on this subject (see the latest in[19][20][21][22][23][24][25]).
[32] Involving excited states, Bersuker also showed that the PJTE is instrumental in explaining the origin of chemical activation and sudden polarization in photochemical reactions.
Another fundamental contribution of Isaac B. Bersuker to the early developments of this field was applying the PJTE to explain the origin of ferroelectricity in perovskite-type crystals.
[35] This first application of the PJTE to solve an important solid-state problem led to developing a whole trend in the studies of local and cooperative properties in crystals.
Using perovskite crystals as an example, Bersuker showed (first in 1964, published in 1966[35]) that the PJTE produces a spontaneous symmetry breaking resulting under certain conditions in local dipolar instability.
Performed in the local octahedral TiO6 center in the BaTiO3 crystal (taken as an example), where vibronic coupling mixes ground 1A1g and close in energy exited 1T1u states of opposite parity (but same multiplicity), detailed analysis with calculations proved the PJTE to produce the dipolar distortion.
[37] According to Bersuker, only the dn cations with the close-energy ground and excited states of opposite parity, but with the same multiplicity, may meet the necessary conditions of ferroelectricity in the presence of unpaired spins.
In a number of his seminal papers, Bersuker introduced and developed theoretical models of vibronic mechanisms in redox properties, electron-conformational effects,[44] chemical reactivity, and catalysis.
[48] Also, Bersuker worked out a quantum mechanics/molecular mechanics method of electronic structure calculations of large organometallic systems when there is charge transfer between the QM and MM parts.