ADIABATIC QUANTUM TUNNELING IN HEAVY-ION SUB-BARRIER FUSION

The measured fusion barrier distributions for {sup 40}Ca+{sup 192}Os, {sup 194}Pt show significant features due to projectile excitation, while none are seen for {sup 16}O+{sup 144}Sm. This conflict is reconciled using realistic coupled-channel calculations, which show that the higher excitation energy of the 3{sup {minus}} state in {sup 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 {ital shape} of a fusion barrier distribution. {copyright} {ital 1997} {ital The American Physical Society}