Berkeley Lab

In Memoriam: Max S. Zolotorev, 1941-2020

By Dmitry Budker, Roger W. Falcone, Derek F. Jackson Kimball, Valeriy V. Yashchuk, and Alexander Zholents

Max Zolotorev

Photo courtesy Felix Izrailev

Retired Berkeley Lab senior scientist Max Samuilovich Zolotorev, a Fellow of the American Physical Society, a pioneer of experimental studies of atomic parity violation, and a generator of ideas across the spectrum of modern physics, passed away on April 1st, 2020 in his home in Eugene, Oregon.

Max was born on October 27, 1941 in Petrovsk, a small town not far from the Russian city of Saratov (on the Volga River), where his mother found herself evacuated from the advancing German army. Max grew up in Kiev, Ukraine. Upon graduating from secondary school, despite showing unusual talent and ability from an early age, since he was Jewish he was not admitted to an institute or even a vocational school. With a friend, he then ventured to Tselina — as part of the Soviet virgin-steppe agricultural development campaign. Upon returning, he worked for about three years at a musical-instrument factory in Kiev, after which, in 1961, he tried his luck in Siberia with the Novosibirsk Electro Technical Institute, where this time he was accepted. After demonstrating outstanding academic performance in his first year, he was able to transfer to the newly founded Novosibirsk State University, from which he graduated in 1966 and assumed a research position at the Institute of Nuclear Physics of the Siberian Branch of the Academy of Sciences of the USSR. There he obtained his first and second doctoral degrees in 1974 and 1979, respectively.

Max started his career as a particle physicist working on measurements of the hyperon magnetic moments. However, in the early 1970s, following a proposal by theorist Iosif B. Khriplovich (who had been four years ahead of Max in the same elementary school in Kiev, and had the same teacher), Max was drawn into studying fundamental physics using the methods of atomic, molecular, and optical physics. Together with his mentor and colleague Lev M. Barkov, he was the first to discover parity violation in atoms by observing optical rotation of the plane of polarization of light propagating through a bismuth vapor. Atomic parity violation — a consequence of the neutral weak interaction between electrons and nuclei — is a key prediction of the Glashow-Weinberg-Salam electroweak unification theory, the core of what is known today as the standard model of particle physics.

Zolotorev and Barkov’s 1978 measurement came at a crucial time in the history of the standard model. While observations of high-energy neutrino scattering on nuclei at CERN in 1973 provided evidence of neutral weak currents, there was no evidence that the neutral weak current violated parity, as predicted by the Glashow-Weinberg-Salam model, at the time of Zolotorev and Barkov’s experiment. Furthermore, earlier atomic parity violation experiments had produced null results, in contradiction to theoretical predictions. The observation of parity violation in bismuth, followed later by measurements of parity violating electron scattering at SLAC and measurements of atomic parity violation in thallium by Eugene Commins and colleagues at the University of California at Berkeley, was crucial evidence that the Glashow-Weinberg-Salam theory was indeed the correct description of the electroweak interaction.

Max and colleagues also established the foundation for some of today’s most sensitive magnetometers with their measurements in the late 1980s of nonlinear Faraday rotation, clearly identifying the crucial role of quantum coherences.

In 1989, Max and his family emigrated from the USSR and, with support from Max’s friend and future collaborator Eugene Commins, found their way to California (via Austria and Italy). After a brief appointment at UC Berkeley, Max assumed a research position at the Stanford Linear Accelerator Center (SLAC). In 1996, he moved to Berkeley Lab, where he worked in the Accelerator Technology and Applied Physics Division until his retirement in 2018.

Upon arriving at SLAC, Max proposed using lasers for cooling hadrons in colliders (a revolutionary idea for that time) as a variation on van der Meer’s stochastic cooling method. Max was the first to foresee that a laser working in tandem with magnetic undulators would be capable of broadening the bandwidth of van der Meer’s microwave system by a factor of a thousand, correspondingly reducing the cooling time. The “optical stochastic cooling” concept formulated by Max, together with Alexander Mikhailichenko and Alexander Zholents, will soon be put to a test at Fermilab by a group led by Max’s former Novosibirsk University student Valeri Lebedev.

Another of Max’s major inventions (in collaboration with Zholents) is the “slicing method” to produce ultrashort pulses of x-rays, essential for time resolved studies of the properties of condensed matter. In slicing experiments, an ultrashort laser pulse “tags” a portion of an electron bunch circulating in a storage ring, and this results in emission of correspondingly short x-ray pulses when the electrons propagate in a periodic magnetic structure. Joined by Robert Schoenlein and other LBNL colleagues, they were first in the world to obtain ~100 femtosecond x-ray pulses with appreciable intensity. Later on, similar capabilities were developed at x-ray facilities in Germany and Switzerland.

Max was an inspiring mentor and teacher who always set the highest expectations for his students. He taught at Novosibirsk University, and had several research students (including Dmitry Budker). Later on, he played a pivotal role in “bringing up” many of his “scientific grandchildren” (including D. F. Jackson Kimball). While working at SLAC and LBNL, Max actively collaborated with Budker’s group at UC Berkeley (including Valeriy V. Yashchuk) and often visited their lab, typically over the weekend. His teaching and mentoring occurred during these visits. His ability to find “weak spots” in one’s scientific logic was legendary.

Some of his wisdom came down in the form of whimsical stories. One particularly memorable dialog between Max and a student started with Max announcing: “Physicists are 3% of rats.” After pondering this for a few moments, the student replied, “Max, what do you mean?” “Look. They did experiment. They put rats in a cage with a high voltage electrode. 27% of rats touch the electrode one time, get shocked, never touch again. 70% of rats watched 27% of rats touch electrode, never touch in first place. But 3% of rats go up to electrode, touch from bottom, get shocked. Then they touch from side, get shocked. Then they touch from other side, get shocked. Then they touch from top, get shocked. They try to figure out what is going on. They are physicist rats.”

One of Max’s great insights was that as physicists, we should never design our experiments around what was sitting in our labs or in our heads. Max would remind us that “We should not be tied to iron!” We should choose deep and important problems, think hard about them, and develop the cleverest way to approach them that we can, learn new subjects, build new apparatus, and push our boundaries and limits as far as we can. Max’s work exemplified the curiosity, creativity, and rigor of physics at its best.

Max Zolotorev is survived by his wife of 55 years Alya, their children Irina and Yakov, and grandchildren Gersh and Giora.