Systematics of Heavy-Ion Fusion Reactions at Extreme Sub-Barrier Energies

概要

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A new measurement of fusion reactions down to 10 nb has been performed for the system ^<64>Ni + ^<64>Ni. Coupled-channels analyses have been carried out for the systems ^<60>Ni + ^<89>Y and ^<64>Ni + ^<64>Ni. They demonstrate that coupled-channels calculations are unable to reproduce the unexpected steep falloff of the cross sections at extreme sub-barrier energies. Heavy-ion fusion excitation functions are also analyzed in terms of the S factor, as this offers a pragmatic way to study fusion behavior in the energy regime of interest. It is shown that the steep falloff in cross section observed in several heavy-ion systems translates into a maximum of the S factor. The energies where the maximum occurs can be parameterized with a simple empirical formula. The parameterization, which is derived here for rather stiff heavy-ion systems, provides also an upper limit for reactions involving softer nuclei.
理論物理学刊行会の論文
2004-07-30