Wilfried Wolfgang Daehnick, a distinguished experimental nuclear physicist and research administrator, died of lymphoma on 24 January 2003 in Pittsburgh, Pennsylvania.
Born in Berlin, Germany, on 30 December 1928, Wilfried managed to pursue his education without major interruptions, despite World War II and its aftermath. In later years, he would speak openly and honestly, and sometimes with wry humor, about what was needed to survive in those difficult times. He received a BS in physics from the Technical University in Munich in 1951 and an MS in physics from the University of Hamburg four years later. In 1958, working with John Fowler, he earned a PhD from Washington University in St. Louis, Missouri, for a study of the reaction d + d → 3He + n. After a postdoctoral position at Princeton University, he joined the faculty of the University of Pittsburgh (Pitt) in 1962, where he became a full professor in 1969.
Wilfried was a masterly experimenter in nuclear physics; his research was characterized by thoroughgoing attention to every aspect, both experimental and theoretical, of each project. He pushed experimental techniques beyond the state of the art. For example, he very early on (1967) developed a large position-sensitive detector incorporating particle identification for the focal plane of the magnetic analysis system. That technique allowed rapid accumulation of data with the highest possible energy resolution. In his work with the accelerators at Pitt from 1962 to 1980, he concentrated on direct nucleon-transfer reactions (stripping and pick-up) to probe nuclear structure in terms of the nuclear shell model. Through distorted-wave Born approximation analysis of stripping (for example), he determined the distribution of a given shell-model single-particle state among the various final nuclear states of the same spin and parity, and by applying sum rules, he measured the degree of occupation of that single-particle state in the target nucleus. Inelastic scattering and (p,nγ) coincidence experiments provided subsidiary information on individual nuclear states. In 1983, he built on that work and produced a major Physics Reports review article on residual interaction matrix elements extracted from data on nucleon-transfer reactions.
By that time, Wilfried was doing transfer experiments at the higher energies available at the Indiana University Cyclotron Facility (IUCF). In 1987, he was among the first users of IUCF to recognize the potential of its new electron-cooled storage ring. His proposal to use the “Cooler” to study pion production in proton-proton collisions marked a shift in his research interest to more fundamental questions, and called for the addition of a large-gap magnetic spectrometer. As it turned out, that spectrometer was to remain the only magnetic separator available to Cooler scientists until the shutdown of the facility in 2002. The spectrometer was an important tool for a number of diverse experiments. Wilfried brought to the IUCF not only a range of equipment for the common use, but also enthusiasm for nuclear physics and intellectual leadership.
In 1995, the Pitt medium-energy group, led by Wilfried and by Steven Dytman, made a precise measurement of the cross section of charged pion production in proton-proton collisions very close to threshold, and followed up by studying the analyzing power of the reaction. Later, the group measured spin correlation coefficients; that measurement used a polarized internal hydrogen target operated by the Polarized Internal Target Experiments (PINTEX) group, a collaboration of researchers from several Midwestern universities.
Wilfried had a rare ability to split his time between administration and research, and to succeed at both, without neglecting his teaching. A strong believer in faculty involvement in university governance, he worked tirelessly to improve budget and computing policies that affected research at Pitt. He often encouraged reluctant faculty to be participants by sounding out their concerns and then asking, “Well, if you don’t like the way it is, why don’t you do something about it?”
In 1989, Wilfried became associate provost for research and then vice provost for research before retiring in 1996. He persuaded the university to set up the Chancellor’s Distinguished Research Award and to adopt an enlightened research allocations policy, which appropriates predictable amounts (based on the overhead paid by research grants) for seeding new research initiatives.
After his retirement, Wilfried returned to research, his first love but for his family, with undiminished enthusiasm. He joined the PINTEX collaboration in 1998, and it was his initiative that led to the first measurement of spin correlation coefficients for pion production in the three-nucleon system at the IUCF. Until the sudden onset of his brief final illness, Wilfried was eagerly working on the analysis of that experiment.
Wilfried’s many friends and colleagues at Pitt and Indiana, especially the members of PINTEX, miss his insightful advice and relaxed and cheerful presence, and are saddened by the loss of a valued colleague.
