Larry Spruch, a prominent theoretical physicist, died on 10 August 2006 in New York City after a long and courageous battle with lung cancer. In a career remarkable for its steady productivity at the highest level, Larry covered a range of research subjects, including nuclear theory, atomic structure, scattering, reaction theory, a quantum electrodynamics (QED) approach to longrange atomic forces, and astrophysics.
Born in Brooklyn on 1 January 1923, Larry received an undergraduate degree in physics in 1943 from Brooklyn College. He earned his PhD in 1948 for his work on the beta decay of the triton under Leonard Schiff at the University of Pennsylvania. For the next two years, he was a postdoctoral fellow at MIT, working with Herman Feshbach and Victor Weisskopf on problems in nuclear physics. Larry then joined the faculty at New York University, which was his home from then on.
In the late 1950s, Larry and his NYU coworkers developed a powerful calculational approach, analogous to the standard Rayleigh–Ritz method for bound states, to atomic few-body scattering problems. The approach’s elegant minimum principles had a significant impact, encouraging theorists that some of the complexities of atomic scattering could be brought under control. Larry and colleagues introduced the Feshbach projection operator formalism to extend the variational-bound approach to positive energies. This formalism, which can be traced directly to Larry’s work with Thomas O’Malley and Yukap Hahn and is now part of the standard equipment of atomic theorists, 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. Larry’s research in this area culminated in a general prescription for constructing variational principles for any quantity of physical interest. With Edward Gerjuoy and others, he cowrote an excellent review on the subject. He summarized his work on rearrangement collisions at high impact velocities in a widely read review paper. In another extraordinary publication, he 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 a seminal 1961 paper on effective-range theory, Larry and his NYU colleagues 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 the modification. This modification was useful for parameterizing data obtained experimentally. With Edward Kelsey, Larry showed that the customary r −4 polarization potential of Rydberg atoms must be supplemented by an 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. Working with James Babb and Martin Schaden, Larry devoted much of his time in the last years of his life to analyzing such retardation effects, primarily as generalizations of the Casimir effect, and gave simple heuristic derivations of results that take many pages to derive using the full formalism of QED.
In 1994 Larry retired from NYU and was appointed as professor emeritus. He continued his physics research, working, as he informed us, “harder than ever.”
Larry 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 as a whole through his review papers, lecture notes, editorial work, and numerous personal interactions. Among the recognitions he received were a senior Humboldt Research Award in 1985 and the American Physical Society’s 1992 Davisson-Germer Prize.
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, also a physicist, published a collection of science quizzes for the layperson. He had a strong social conscience and could be scathingly caustic of excesses and injustices in the public sphere.
We also recall hiking with Larry and Grace in the Rockies near Aspen, Colorado, where the two often escaped New York City summers. Even during his illness, he maintained his interest in physics; in fact, he was “doing” physics with Schaden the night before he was hospitalized for the final time. In all encounters, Larry’s cheerfulness, enthusiasm, marvelous sense of humor, and zest for life made him a wonderful companion and an exceptional mentor.
