Experimental nuclear and radiochemistry. Progress report, February 1, 1979-January 31, 1980

This project entails the investigation of deep nuclear spallation reactions induced by high-energy light particles on complex nuclei. Experimental studies involve activation of various medium- to heavy-mass targets bombarded by pi mesons, protons, and alpha particles. A prime objective is to deconvolve the cascade and evaporation steps in the reaction mechanism. Experimentally, then, particular emphasis has been placed on spallation products far from yield maxima. Irradiations have been performed predominantly at the Clinton P. Anderson Los Alamos Meson Physics Facility. Results from bombardments of 89Y with 190-MeV π-, 800-MeV protons and 720-MeV alphas (SREL) have been nearly completed; mass-yield distributions were compared. Pion-induced neutron removal reactions have been presented for 90Zr and 96Ru along with a serious critique of the final-state charge interaction hypothesis. Theoretical efforts are being directed at the evaporative behavior of very high-temperature nuclei as determined by the nuclear equation of state and how such behavior might become evident in spallation processes. In addition, the soft spheres model has been extended to consider the significance of nuclear transparency in high-energy reactions