Energy dependence of nucleus-nucleus potential close to the Coulomb barrier

Abstract

The nucleus-nucleus interaction potentials in heavy-ion fusion reactions are extracted from the microscopic time-dependent Hartree-Fock theory for mass symmetric reactions ${}^{16}$O${+}^{16}$O, ${}^{40}$Ca${+}^{40}$Ca, ${}^{48}$Ca${+}^{48}$Ca and mass asymmetric reactions ${}^{16}$O${+}^{40,48}$Ca, ${}^{40}$Ca${+}^{48}$Ca, ${}^{16}$O+${}^{208}$Pb, ${}^{40}$Ca+${}^{90}$Zr. When the center-of-mass energy is much higher than the Coulomb barrier energy, potentials deduced with the microscopic theory identify with the frozen density approximation. As the center-of-mass energy decreases and approaches the Coulomb barrier, potentials become energy dependent. This dependence signs dynamical reorganization of internal degrees of freedom and leads to a reduction of the "apparent" barrier felt by the two nuclei during fusion of the order of $2-3$ compared to the frozen density case. Several examples illustrate that the potential landscape changes rapidly when the center-of-mass energy is in the vicinity of the Coulomb barrier energy. The energy dependence is expected to have a significant role on fusion around the Coulomb barrier.

11 pages, 13 figures, 1 table, discussion of effects of coordinate-dependent mass added, accepted for publication in Phys. Rev. C

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