Hot fusion-evaporation cross sections of Sc45-induced reactions with lanthanide targets
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© 2015 American Physical Society. Background: Sc45 has rarely been studied as a projectile in fusion-evaporation reactions. The synthesis of new superheavy elements with Z>118 will require projectiles with Z>20, and Sc45 could potentially be used for this purpose. Purpose: Cross sections were measured for the xn and pxn exit channels in the reactions of Sc45 with lanthanide targets for comparison to previous measurements of Ca48 reacting with similar targets. These data provide insight on the survival of spherical, shell-stabilized nuclei against fission, and could have implications for the discovery of new superheavy elements. Methods: Beams of S45c6+ were delivered from the K500 superconducting cyclotron at Texas A&M University with an energy of ≈5MeV/nucleon. Products were purified using the Momentum Achromat Recoil Spectrometer, and excitation functions were measured for reactions of Sc45+Gd156-158,160, Tb159, and Dy162 at five or more energies each. Evaporation residues were identified by their characteristic α-decay energies. Experimental data were compared to a simple theoretical model to study each step in the fusion-evaporation process. Results: The maximum measured 4n cross sections for the reactions Sc45+Gd156-158,160, Tb159, and Dy162 are 5.8±1.7, 25±5, 39±7, 150±20, 2.4-1.4+2.3, and 1.8±0.6μb, respectively. Proton emission competes effectively with neutron emission from the excited compound nucleus in most cases. The α,αn, and α2n products were also observed in the Sc45+Dy162 reaction. Conclusions: Excitation functions were reported for Sc45-induced reactions on lanthanide targets for the first time, and these cross sections are much smaller than for Ca48-induced reactions on the same targets. The relative neutron-deficiency of the compound nuclei leads to significantly increased fissility and large reductions in the survival probability. Little evidence for improved production cross sections due to shell-stabilization was observed.
author list (cited authors)
Werke, T. A., Mayorov, D. A., Alfonso, M. C., Bennett, M. E., DeVanzo, M. J., Frey, M. M., Tereshatov, E. E., & Folden, C. M.