Shimon Vega, 1943-2021

It is with great sadness that we report the recent passing of Shimon Vega at age 78.  Shimon was widely recognized for his many contributions to magnetic resonance, especially to the conceptual basis of modern solid state NMR, and for the clarity of his thoughts and presentations.  He was a Fellow of ISMAR and the recipient of the 2015 ISMAR Prize.  The following obituary was written by his colleagues Daniella Goldfarb and Lucio Frydman:

Shimon Vega was born in Amsterdam on November 14, 1943 and passed away two days after his 78th birthday.  As he would later say: “This was not a good time and place for a Jewish child to be born, and led to what perhaps was the most ‘interesting’ part of my life”.  At the age of 6 weeks he was sent to a hideout with a Dutch family until the end of the war, thus surviving the Holocaust. He grew up in Ouderkerk aan de Amstel, a small village south of Amsterdam. After obtaining both his B.Sc. and M.Sc. in Physics in Holland he moved to Israel with his wife Margrit, and completed his Ph.D. with Prof. Zeev Luz at the Weizmann Institute on Nuclear Quadrupole Resonance.  Shimon stood out already during his PhD, where he published his thesis papers as a sole author with the full encouragement of his advisor. This work was the beginning of a joint tackling of the theoretical and experimental chemical physics underlying magnetic resonance.  After PhD graduation Shimon became Alex Pines’ first postdoc at Berkeley, where they made pioneering discoveries in the new field of multiple-quantum NMR. This work would eventually lead to setting the basis for the fictitious-spin-½ formalism, nowadays a primary tool for understanding NMR in solids and liquids and gaining recognition in EPR and quantum optics.

Upon completing his postdoc Shimon returned as a tenure-track faculty to the Weizmann Institute, where he expanded these studies to half-integer quadrupolar nuclei. This work, along with the multi-quantum concept, served as basis for additional future developments in the field that resulted in a wide variety of materials-oriented research.  Shimon continued to focus mostly on solids NMR and developed new decoupling and recoupling methods, as well as new kinds of pulses and new structural determination schemes –most often while relying on magic angle spinning (MAS). In those late-1970/early-1980 days, MAS was largely viewed from a continuous-wave perspective; i.e., as an averaging process leading to the cancelation of second-rank anisotropies and hence sharp spin-1/2 lines. Drawing from the time-domain perspective that had led to multiple-quantum NMR, Shimon departed from this outlook, and was among the first to recognize the complex time-dependencies that underlie MAS as an averaging process. Starting at Weizmann and furthering these ideas during sabbaticals at MIT with R.G. Griffin and at Washington University with J. Schaefer in the 1980s, Shimon thus developed sophisticated theories –many of them based on the Floquet formalism– to advance the understanding of MAS NMR. These efforts allowed exact computation of MAS spectra under a variety of scenarios, while leading to a deeper understanding and to new pulse sequences. They also lead to new methods to evaluate dynamic processes in MAS NMR, and to the design and interpretation of a variety of discrete multipulse recoupling experiments. The latter included homo- and hetero-nuclear dipolar decoupling/recoupling schemes like SEDRA, TEDOR, RFDR and REAPDOR, that have since become common tools in the biomolecular and materials NMR arsenal. They also included sensitivity enhancement schemes, such as the FAM sequence for semi integer quadrupolar nuclei. During  a  subsequent  stage  of  Shimon’s  solids  NMR  research  he  extended Floquet’s sophisticated formalism to a multimodal format, capable of accounting for the coherent evolution of a density matrix subject to multiple, non-commensurate time-dependent processes simultaneously. Numerous experiments he designed were on the basis of multi-modal Floquet theories, in particular the high resolution single- and multidimensional proton NMR phase-modulated Lee-Goldburg sequences (PMLGn).

During the last decade Shimon embarked on yet another venture: understanding the mechanism of dynamic  nuclear  polarization (DNP) at high magnetic fields.  He realized the limitation of traditional steady-state descriptions of DNP, and developed instead quantum mechanical models which could reproduce and predict important experimental features – helping to bring about DNP MAS NMR’s renaissance. Shimon continued to be highly active and productive years after his “formal” retirement, and kept working on and thinking about magnetic resonance till the day he was hospitalized.

Shimon was truly exceptional as an educator and scholar, that molded and enriched the lives of those he met and interacted with. He was an engaging lecturer that would capture audiences, despite –and perhaps because of– his relentless refusal to escape from equations and meaningful concepts. He was a sought-after teacher that in addition to regular courses at the Weizmann Institute devoted ample time lecturing at high schools, guiding local kids in visits through the Weizmann labs, and sharing his science with his community –much before outreach activities became “fashionable”. Shimon was a remarkable mentor, who trained graduate students and postdoctoral fellows that are now leaders in the forefront of magnetic resonance worldwide. But more than anything else, Shimon was an exceptionally caring human being, who inspired with his generosity in sharing his knowledge and wisdom, his patience, his unusual capability to listen, and his modesty. At the Israel Chemical Society 2018 meeting, which endowed Shimon with its highest Gold Medal award, Shimon summed up some of these traits in a way that reflected his personality: “I wish to share with you, my love. Above all my love for my wife Margriet, who in addition to all the rest, made it possible for me to dedicate much of my time to science. And for our children who knew what it meant to have a dad in the lab or abroad or in miluim  (army reserve). Let me tell you about my other love… Magnetic Resonance… I wish to thank the ICS Prize Committee. I assume that if I had been a member of that committee, I would not have voted in favor of myself. Why? Because I know what I know and I also know what I don’t know, but they don’t realize how much I don’t know. It is a great honor for me to join the incredible list of ICS Gold Medalists.”

We will miss Shimon greatly, but consider ourselves fortunate to have had him as fellow traveler during the course of our journey through science and life.

Daniella Goldfarb and Lucio Frydman

Rehovot, November 2021