Adiabatic Quantum Tunneling in Heavy-Ion Sub-barrier Fusion

Abstract

High precision measurements of the fusion excitation functions for the reactions 40 Ca 192 Os clearly demonstrate that projectile excitation significantly modifies the potential barrier distribution. In sharp contrast, fusion of 16 O + 144 Sm appears to show no influence of the projectile excitation on the shape of the barrier distribution. These apparently conflicting conclusions are reconciled in this work, using realistic coupledchannels calculations, which show that high energy states produce an adiabatic potential renormalisation. This result indicates that adiabatic effects restrict, in a natural way, the states which influence the shape of a fusion barrier distribution. The analysis of barrier distributions thus offers a criterion for the relevance of the 'counter term' prescription in the Caldeira-Leggett approach.

Sub-barrier fusion enhancement with radioactive134Te

“…An issue to be discussed in the systematic comparison of the reduced excitation functions [ Fig. 3(a)] is the strength of the octupole mode in 40 Ca which can produce a potential renormalization of the barrier [35]. This was demonstrated by Stefanini et al for Ca + Zr systems [12].…”

“…The curvature of the barrier ( ω) defines a limit for which states need to be included in the coupled-channel calculations [35]. Since the energy of the 3 − state in 40 Ca is roughly equal to the curvature of the barrier it was included in the coupling scheme [35].…”

Examining the role of transfer coupling in sub-barrier fusion ofTi46,50+Sn124

“…8(a). It is worth noting that the coupling to the octupole state in 40 Ca also results in a barrier well below the uncoupled barrier for other reactions [31][32][33].…”

Coupled–Channels Analyses For Heavy–Ion Fusion Reactions of ¹⁶O+⁹²Zr,^144,148Sm Systems

“…Instead of such approaches, here we perform the coupled-channels calculations using an error function type potential for the nuclear potential. The aim of this study is to see weather this approach works to explain the fusion data of 16 O+ 92 Zr, 144,148 Sm reactions [12,13]. In particular, we study the effects of multiphonon excitations of the target nuclei on the fusion cross sections as well as the fusion barrier distributions for these systems.…”

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We study in detail the fusion reaction of 16 O with 92 Zr and 144,148 Sm at sub-barrier energies with coupled-channels framework using the error function potential for the nuclear potential. In particular, we investigate the effects of multiphonon excitations in target nuclei on experimental fusion cross section and barrier distributions for these reactions.

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