Richard Bersohn, a chemical physicist best known for his elegant, powerfully simple studies of molecular photodissociation and chemical kinetics, died of cancer on 18 November 2003 in New York City. He was the Higgins Professor of Natural Science at Columbia University.Born 13 May 1925 on the Upper West Side of Manhattan in New York City, Richard earned his BS in chemistry from MIT at age 19. After receiving his degree, he entered the US Army, passed through basic training, and then worked on chemical separations at Clinton National Laboratory (now Oak Ridge National Laboratory) as part of the Manhattan Project.Deeply interested in physics, Richard began his theoretical studies in 1946 as a student of John Van Vleck at Harvard University. He did his PhD thesis on dipole interactions in nuclear magnetic resonance (NMR), which had just been discovered in Edward Purcell’s laboratory at Harvard. In 1949, he took a postdoctoral fellowship in theoretical quantum electrodynamics with Willis Lamb at Columbia and in 1951, began his academic career at Cornell University. He moved back to Columbia in 1959 to become a professor of chemistry, and remained at Columbia for 44 years. He held an adjunct appointment at the Weizmann Institute of Science, in Rehovot, Israel, where he spent his summers for many years, and had strong, long-lasting collaborations in both that country and in Japan.At Cornell, Richard started research work in theory, but as computers came of age, he realized that he did not enjoy numerical work. He would sometimes quote Peter Debye, with whom he interacted at Cornell, who said, “You should understand the physics, write down the correct equations, and then let Nature do the calculations.” With his first Cornell students, he began experiments in molecular physics and spent a sab-batical, beginning in 1958, working on the optical pumping field with Alfred Kastler at the École Normale Supérieure.At Columbia, Richard established experimental groups in optical probes of molecular kinetics and in biophysics. A pioneer in biophysics, he used both Förster energy transfer and NMR methods to study the tertiary structure of proteins. Having recognized quite early the value of short-pulse lasers in biology, he collaborated in that area with Peter Rentzepis and with Erich Ippen and Charles Shank at Bell Labs in Murray Hill, New Jersey, where Richard was a long-standing consultant.In molecular kinetics, Richard invented “photolysis mapping,” which reveals the symmetry of the excited state in a photodissociation process through the relative spatial pattern of the resultant fragments. That experiment, which came simultaneously with the molecular beam revolution in chemical kinetics, had a deep effect on the entire community of photo-chemists and photophysicists. It was a forerunner of modern multidimensional product velocity mapping.Richard was a quiet and gentle soul who was widely respected in both the molecular physics and chemistry communities. He was a minimalist in his personal and professional life, shunning fluff and venality. As a boy, his great enthusiasm was for experiments, and he never lost that youthful fascination. Almost two years before his passing, he wrote his scientific memoirs in volume 54 of the Annual Review of Physical Chemistry , and that fascination animates his recollections. Richard’s understanding of chemistry and physics was deep and broad, and his colleagues invariably turned to him for advice on any new project.An insightful judge of people and ideas, Richard was instrumental in building the chemical physics community at Columbia during his long academic career. He showed leadership and scientific courage by personal example and gave his students the freedom to explore—and to learn from their failures—in their scientific endeavors. He championed the cause of the junior faculty and gave freely of his time not only to the Columbia chemistry department, but also to the wider scientific community. Anyone felt fortunate to be among Richard’s friends.In 1985, Richard won the American Physical Society’s Herbert P. Broida Prize. He was head of APS’s division of chemical physics in 1971 and chair of the advisory committee to Brookhaven National Laboratory’s chemistry department (1981–84). He was chairman of the chemistry department at Columbia (1990–93) and associate editor for chemical physics for Physical Review Letters (1995–98). He had been planning to retire in 2004.A scientist, colleague, and mentor of exceptional intellectual creativity and talent, Richard is sorely missed by his family, friends, and the scientific community.Richard BersohnCOLUMBIA UNIVERSITYPPT|High resolution© 2004 American Institute of Physics.
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