Obituary of Larry Spruch

Larry Spruch, a prominent theoretical physicist, died on 10 August 2006 after a long and courageous battle with lung cancer.

Born in Brooklyn on 1 January 1923 Larry received an undergraduate degree from Brooklyn College in 1943. His thesis work (Ph.D, 1948) at the University of Pennsylvania was done with L. Schiff on the beta decay of the triton. The next two years were spent as a Postdoctoral Fellow at MIT, working on problems in nuclear physics with H. Feshbach and V. Weisskopf. Larry then joined the faculty at New York University which was his home from then on. After retirement, and appointment as Professor Emeritus in 1994, he continued his physics research, working, as he informed us, “harder than ever.”

In a career remarkable for its steady productivity at the highest level, Larry’s research covered a wide range of subjects including nuclear theory, atomic structure, scattering, and reaction theory, a QED approach to long-range atomic forces, as well as topics in astrophysics. Beyond this, he was an intellectual leader and teacher, not only to the many students and research associates who were trained by him but, in a sense, to the community a whole through his review papers, lecture notes, editorial work and numerous personal interactions. A senior Humboldt Award in 1985 and the Davisson-Germer prize in 1992 were recognitions of his many contributions.

In the late 1950s Larry, along with his NYU co-workers, developed a powerful calculational approach to atomic few-body scattering problems analogous to the standard Rayleigh-Ritz method for bound states. These elegant minimum principles had a significant impact, encouraging theorists that some of the complexities of atomic scattering could be brought under control. The Feshbach projection operator formalism was introduced to extend the variational-bound approach to positive energies. This formalism is now part of the standard equipment of atomic theorists and led to striking success in the analysis of Feshbach resonances in atomic reactions, a development that was crucial to the field of laser-atom cooling. It can be traced directly to Larry’s work with T.F. O’Malley and Y. Hahn. Larry’s research in this area culminated in a general prescription for constructing variational principles for any quantity of physical interest. With E. Gerjuoy and others, he is co-author of an! excellent review on this subject. His work on rearrangement collisions at high impact velocities was summarized in a widely read review paper. In yet another extraordinary RMP publication Larry gave a lucid account of Thomas-Fermi theory and its application not only to atoms but also to problems concerning neutron stars, white dwarfs, QED and the stability of bulk matter.

In 1961 Larry and co-workers wrote a seminal and widely referenced paper on effective-range theory. They showed that the polarizability of an atom results in a significant modification to the phase shift for low energy electron-atom scattering, and they worked out this modification. This was very useful for parametrizing data obtained experimentally. With E. Kelsey he showed that the customary r^{-4} polarization potential must be supplemented by a r^{-5} interaction when the time it takes light to travel from the Rydberg electron to the core is comparable to a Rydberg orbital period. Larry devoted much of his time in the last years (working with J. Babb and M. Schaden) to an analysis of such retardation effects, primarily as generalizations of the Casimir effect, and was extremely successful in giving simple heuristic derivations of results that take many pages to derive using the full formalism of QED.

We who were privileged to know and interact closely with Larry also remember his readiness for discussion and argument in and out of physics. He had an interest in puzzles and quizzes and, with his wife Grace, herself a physicist, published a collection of science quizzes for the layman. He had a strong social conscience and could be scathingly caustic of excesses and injustices in the public sphere.

Many of us also recall hikes in the Rockies near Aspen, where he and Grace often escaped New York City summers. In all these encounters, Larry’s cheerfulness, enthusiasm, marvelous sense of humor, and zest for life made him a wonderful companion besides being a mentor. Even in the illness of his last years he maintained his interest and was “doing physics” with Martin Schaden the night before his admission to the hospital for the last time. We felt great affection for Larry and will miss him.