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

High-spin states have been studied in the octupole-deformed [sup 222]Th nucleus using the [sup 208]Pb([sup 18]O,4n) reaction. Deexcitation 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 gammaray energy detected in the reaction is less than 10 MeV, the intensity of [sup 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. [ABSTRACT FROM AUTHOR]