Abstract
We demonstrate the damping of quantum octupole vibrations near the touching point when two colliding nuclei approach each other in the mass-asymmetric $^{208}$Pb + $^{16}$O system, for which the strong fusion hindrance was clearly observed. We, for the first time, apply the random-phase approximation method to the heavy-mass asymmetric di-nuclear system to calculate the transition strength $B$(E3) as a function of the center-of-mass distance. The obtained $B$(E3) strengths are substantially damped near the touching point, because the single-particle wave functions of the two nuclei strongly mix with each other and a neck is formed. The energy-weighted sums of $B$(E3) are also strongly correlated with the damping factor which is phenomenologically introduced in the standard coupled-channel calculations to reproduce the fusion hindrance. This strongly indicates that the damping of the quantum vibrations universally occurs in the deep sub-barrier fusion reactions.
Highlights
At extremely low incident energies, called the deep subbarrier energies, the steep fall-offs of fusion cross sections compared to the estimations of the standard coupledchannel (CC) model have been observed in a wide range of mass systems
An important observation for understanding this fusion hindrance is that the potential energy at the touching point of the colliding nuclei strongly correlates with the threshold incident energy for the emergence of the fusion hindrance
In this paper, I would like to stress that the treatment of the coupling potential in the overlap region is much important for describing the deep sub-barrier fusion hindrance
Summary
At extremely low incident energies, called the deep subbarrier energies, the steep fall-offs of fusion cross sections compared to the estimations of the standard coupledchannel (CC) model have been observed in a wide range of mass systems (see Ref. [1] for details). The fusion hindrance would be associated with dynamics in the overlap region of the two colliding nuclei The other is the adiabatic approach proposed by Ichikawa et al [6] In this approach, neck formations between the colliding nuclei are taken into account in the overlap region. Neck formations between the colliding nuclei are taken into account in the overlap region Based on this picture, the sudden and adi-. In this paper, I would like to stress that the treatment of the coupling potential in the overlap region is much important for describing the deep sub-barrier fusion hindrance.
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