Measurement of evaporation residue cross-sections of the reaction 30Si + 238U at subbarrier energies
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The reaction 30Si + 238U → 268Sg* was studied at beam energies close to the Coulomb barrier. At a center-of-mass energy of Ec.m. = 144.0MeV for reactions at half thickness of the target we measured three decay chains of 263Sg produced by evaporation of five neutrons. The cross-section was ( 67+67-37) pb. At Ec.m. = 133.0MeV we measured three spontaneously fissioning nuclei which we assigned to the isotope 264Sg. The production cross-section was ( 10+10-6) pb and a half-life of ( 120+126-44) ms was determined. This half-life is a factor of twenty shorter than theoretical predictions. At Ec.m. = 128.0MeV an upper cross-section limit of 15pb was measured. The cross-section data reveal a strong influence of the orientation of the deformed target nucleus on the production yield. Compared to excitation functions measured for the lighter system 16O + 238U → 254Fm*, a reduction of the fusion probability was observed at low beam energies indicating increasing competition from quasifission processes.
PACS.25.60.Pj Fusion reactions 23.60.+e α decay 25.85.Ca Spontaneous fission 27.90.+b 220 ⩽ A
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