Entrance Channel in Heavy-ion Reactions for Superheavy Element Production

We discuss both cold fusion reactions of the type that lead to the formation of elements with proton number Z from 107 to 113 and hot fusion, that is reactions with deformed actinide targets [1]. In cold fusion with Pb-like targets we show that for reactions eading to the heavier evaporation residues deformation and shell effects lead to a fusion barrier that is more than 10 MeV lower that what is obtained in a standard spherical macroscopic liquid-drop model. Inside touching we calculate the macroscopic-microscopic potential energies of the composite system in a five-dimensional deformation space consisting of about 4 million nuclear shapes. We find that the composite system exhibits a well-established fusion channel in which the initial composite shape closely matches the shape-polarized shapes just outside touching. In hot-fusion reactions that target is deformed and experimental and theoretical considerations indicate that ``equatorial'' collision are the most likely to lead to evaporation residue formation. Also in this case we show that shape polarizations lead to a significant decrease of the equatorial fusion barrier. [1] T. Ichikawa, A. Iwamoto, P.M\"oller, A. J. Sierk, Phys. Rev. C {\bf 71}, 044608 (2005).