Enhancement and Suppression of Fusion in Reactions Forming Heavy Nuclei

A new framework for comparing fusion probabilities in reactions forming heavy elements is presented, that eliminates both theoretical and experimental uncertainties, and gives new insights into systematic behavior. This should help in predicting favorable reactions to form new heavy nuclei. The framework is firstly applied to the formation of isotopes of Thorium, where it is found that production yields follow a simple systematic behavior. The data consistently show that fusion is inhibited (presumably by quasi-fission) by about a factor of 10 for projectiles ranging from Ar to Sn, with little dependence on shell structure in the projectile, target or compound nuclei. Application to formation of isotopes of Nobelium shows much more drastic changes in fusion probability as a function of entrance-channel conditions