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Obituary of Daniel Sperber

14 October 2010

Daniel Sperber, a prominent nuclear theorist, succumbed to a debilitating illness on August 15, 2009 in Geneva, New York. He was part of a generation fated to endure the multiple hazards of ‘living in interesting times’. Dan was born on May 8, 1930 at Vienna, Austria during a maternal excursion arranged by his father, a medical radiologist. The family's acutal residence was in Stanislawow, the provincial seat of a Polish agricultural region situated near the Ruthenian Border. Dan's initial contact with education was through a program of home schooling.

In September of 1939 Poland was overrun by the German blitzkrieg, but the Sperber family evaded capture through fortunate preparations. The maternal grandfather was wealthy, foresighted, and an ardent Zionist. As early as 1933 he had traveled to Palestine and acquired extensive property; two years later he established two of his children in the future land of Israel. Consequently, during the turbulent days immediately following the German onslaught, the Sperbers were able to flee to Romania, reached a Black Sea port, and embarked for Haifa in Palestine.

Although shielded from the most serious effects of the desert campaigns of the Second World War, Dan's adolescent years were cut short by the struggles leading to Israel's War of Independence. The family lived in Jerusalem when the city was occasionally under siege. In 1948 he joined the (illegal) Haganah, and later was co-opted for service in the regular Israeli Defense Forces. He participated in some of the battles for Jerusalem as a sniper while still a senior in High School. After the cessation of overt hostilities Dan was discharged from the military, and enrolled at the Hebrew University in Jerusalem. He graduated with an MCE (Master's) degree in Physics. In 1955 he commenced graduate studies at Princeton Universty (NJ). he was awarded the Ph. D. (Physics) in 1961 with a dissertation entitled “Nuclear States with High Angular Momenta and their Stability” supervised by John A. Wheeler. This work anticipated the direction of much of his future research.

Dan began his post-graduate career with joint appointments in the Physics department of Illinois Institute of Technology (IIT) and the neighboring IIT Research Institute (IITRI) in Chicago. In 1967 he accepted a position as Associate Professor of Physics at Rensselaer Polytechnic Institute in Troy, New York. He was promoted to full Professor in 1972, and served until his retirement in May 2005. Dan was a popular teacher and research leader, attracting students at RPI and, thanks to his background, developing many collaborations with overseas colleagues. As a result, he spent a year as Nordica Professor at the Niels Bohr Institute in Copenhagen, working with his friend Aage Bohr. He was also awarded a Fulbright Fellowship and stayed for a year at the Saha Institute of Nuclear Physics in Calcutta. Other fellowships enabled Dan to visit the Nuclear Physics Department of the Darmstadt Technical University during the summer of 1983. In addition, he was the recipient of a three-year NATO fellowship for nuclear theory. His contributions to numerous national and international conferences—mainly concerned with heavy ion physics—were always substantial.

Dan's earlier publications on the basic features of semi-classical models of strongly damped collisions between heavy ions, and on angular momentum contraints for heavy ion fusion, using proximity potentials, created the basis for his future activities in the field, and are still cited in the contemporary literature. He published papers dealing with nucleon and pion emission from ‘hot’ compressed zones (or ‘hot spots’) in intermediate energy heavy ion collisions. He also studied classical dynamical models including shape deformations describing strongly damped collisions accompanying fusion and incomplete fusion. Further refinements included the effects of inertia and wall friction in heavy ion fusion and strongly damped collisions. Dan investigated the role of thermal fluctuations in fission and the associated scission dynamics. Other research topics included the temperature dependence of nuclear transport coefficients; nucleon spectra in heavy ion collisions prior to equilibration; the role of single particle components in heavy ion fusion; and a microscopic treatment of Pauli blocking in strongly dampened collisions. Especially notable is an elegant determination of the nuclear equation of state by means of the quantum virial theorem.

Dan is survived by Ora, his wife of forty-six years, and his son Ron (Laura), grandson Nathan Daniel, and a step-daughter Tammy Baran. His ironic wit, cosmopolitan outlook, and deep understanding of physics will be missed by many friends and colleagues.

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