High-Spin Study Of Octupole-Deformed ~(222)Th And Reduction Of The Background From Prompt Fission

摘要

High-spin states have been studied in the octupole-deformed ~(222)Th nucleus using the ~(208)Pb(~(18)O,4n) reaction. De-excitation gamma rays were detected using the Euroball-IV gamma-ray spectrometer. The large background of gamma rays from prompt fission fragments, which generally hampers the spectroscopy of actinide nuclei in fusion-evaporation reactions, has been reduced using the Euroball-IV inner BGO ball as a sum-energy filter. With the requirement that the summed gamma-ray energy detected in the reaction is less than 10 MeV, the intensity of ~(222)Th gamma-rays, relative to the prompt fission background is significantly improved. The experiment and data analysis are discussed, and preliminary spectroscopic results are presented.