Adiabatic Quantum Tunneling in Heavy-Ion Sub-barrier Fusion

Abstract

The measured fusion barrier distributions for $^{40}C\mathrm{a}+^{192}O\mathrm{s}$, ${}^{194}$Pt show significant features due to projectile excitation, while none are seen for $^{16}O+^{144}S\mathrm{m}$. This conflict is reconciled using realistic coupled-channel calculations, which show that the higher excitation energy of the ${3}^{\ensuremath{-}}$ state in ${}^{16}$O produces an adiabatic potential renormalization, without affecting the structure in the barrier distribution. This result indicates that adiabatic effects restrict, in a natural way, the states which influence the shape of a fusion barrier distribution.