Applicability of the orientation average formula in heavy-ion fusion reactions of deformed nuclei - art. no. 044603

In heavy-ion fusion reactions involving a well-deformed nucleus, one often assumes that the orientation of the target nucleus does not change during t he reaction. We discuss the accuracy of this procedure by analyzing the exc itation function of the fusion cross section and the fusion barrier distrib ution in the reactions of Sm-154 target with various projectiles ranging fr om C-12 to Ar-40. It is shown that the approximation gradually loses its ac curacy with increasing charge product of the projectile and target nuclei b ecause of the effects of finite excitation energy of the target nucleus. Th e relevance of such inaccuracy in analyzing the experimental data is also d iscussed.