Measurement of Evaporation Residue and Fission Cross Sections of the Reaction ^<30>Si + ^<238>U at Subbarrier Energies
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Effects of the prolate deformation of <SUP>238</SUP>U on fusion were studied in the reaction <SUP>30</SUP>Si + <SUP>238</SUP>U at bombarding energies close to the Coulomb barrier. The fission (capture) cross sections were measured at the JAEA tandem accelerator to see the enhancement of the cross sections in the subbarrier energy due to the lower Coulomb barrier in the collisions of projectile at the polar sides of <SUP>238</SUP>U. In order to obtain the direct evidence for complete fusion, evaporation residue cross sections were measured at UNILAC of GSI. At the subbarrier energy of E<SUB>c.m. </SUB> = 133. 0 MeV, where only polar collisions to <SUP>238</SUP>U occur, we measured three spontaneously fissioning nuclei which we assigned to the isotope <SUP>264</SUP>Sg. The obtained cross section (10<SUP>+10</SUP><SUB>-6</SUB>) pb was smaller than the calculation that the system captured at the polar collisions results in complete fusion, suggesting the competition between fusion and quasifission. At the above barrier energy of E<SUB>c.m. </SUB> = 144.0 MeV, where collisions on the equatorial side of <SUP>238</SUP>U start to contribute, we observed α-decay chains starting from <SUP>263</SUP>Sg and the cross section was determined to be (67<SUP>+67</SUP><SUB>-37</SUB>) pb. The data was reproduced by the calculation that the system captured from the equatorial side of <SUP>238</SUP>U results in complete fusion .
- Journal of Nuclear and Radiochemical Sciences
Journal of Nuclear and Radiochemical Sciences 8(2), 73-78, 2007-12-01
The Japan Society of Nuclear and Radiochemical Sciences