Heavy ion fusion: Possible dynamical solution of the problem of the abnormally large diffuseness of the nucleus-nucleus potential

Abstract

We attempt to make some progress in the problem of the apparently large diffuseness of the Woods-Saxon strong nucleus-nucleus interaction potential (SnnP) needed to fit a large number of precision fusion excitation functions. This problem has been formulated in Newton et al. [Phys. Lett. B 586, 219 (2004);Phys. Rev. C 70, 024605 (2004)]. We applied the classical dissipative trajectory model to describe the data on fusion (capture) of ${}^{16}\mathrm{O}$ with ${}^{92}\mathrm{Zr},$ ${}^{144}\mathrm{Sm},$ and ${}^{208}\mathrm{Pb}.$ No fluctuations or dynamical deformations of the interacting nuclei are accounted for. The friction force is supposed to be proportional to the squared derivative of the SnnP (the surface friction model). The SnnP is calculated within the framework of the double-folding model with the density-dependent M3Y $NN$ forces. This potential is known to possess rather small diffuseness in contradistinction to what is required by the data analysis in Newton et al. [Phys. Lett. B 586, 219 (2004);Phys. Rev. C 70, 024605 (2004)]. Varying slightly the strength of radial friction (universally for all three reactions) and the diffuseness of the charge density of ${}^{208}\mathrm{Pb}$ we have obtained satisfactory agreement of the calculated excitation functions with the data.