This award supports Professor Lawrence Fagg of the Catholic University of America for two short term research visits to the National Institute for Nuclear Physics and High Energy Physics (NIKHEF) in Amsterdam, the Netherlands, where he is collaborating with Dr. C. W. deJager, group leader in the electron scattering program. NIKHEF, the University of Virginia, Catholic University and the Free University of Amsterdam are cooperating in a set of experiments to determine the occupation probabilities for protons in the 2s-1/2 shell. Dr. Fagg's contribution to the program has been supported to a very limited extent by the NSF Physics division. Support for two more trips from the U.S.-Netherlands Cooperative Science Program will enable him to complete the remaining phases of the program. This involves constructing, transporting and mounting delicate samples (targets) of Phosphorus- 31 and Sulfur-32 for exposure to the electron beam of the accelerator. He will also participate in further elastic electron scattering studies on these nuclei plus Silicon-30, acquiring the remaining (e,e'p) data necessary to complete the analysis, and participating in the analysis and interpretation of the data. The Independent Particle Shell Model assumes the nucleus to consist of nucleons moving independently in a common potential well. This model has enjoyed considerable success in explaining many essential features of nuclear structure. One of the most definitive test of IPSM is to observe the behavior of penetrating nucleon orbits in medium and heavy nuclei. In a series of experiments performed at several accelerator laboratories, it was determined that despite the relatively close spacing of nucleons in nuclear matter, the wave function for the 3s-1/2 proton orbit in such nuclei as Lead-206 and Lead-208 was clearly observable. Dr. Fagg is collaborating with Dr. deJager in extending this work to the 2s-1/2 shell for Silicon-30, Phosphorus-31, and Sulfur-32. Although the value of exclusive electron scattering reactions for such studies, in particular the (e,e'p) reactions, has long been known, it is only with the advent of high resolution, higher-duty- factor accelerators such as those at Saclay and NIKHEF that this reaction can now be adequately exploited. There are no facilities in the U.S. with instrumentation of sufficient resolution to carry out the proposed measurements. NIKHEF is contributing ninety hours of beamtime for the project.
