Inverse quasifission in the reactions 156,160Gd+186W

Background: Low-energy multinucleon transfer reactions may be used for production of new neutron-enriched heavy nuclei. Purpose: Our aim is to investigate the influence of proton (Z = 82) and neutron (N = 82, 126) shells as well as orientation effects on the formation of reaction products in the inverse quasifission process in the reactions Gd-156,Gd-160 + W-186. Methods: Mass, energy, and angular distributions of primary binary fragments formed in the reactions Gd-156 + (186)Wat an energy of 878 MeV, and Gd-160 + (186)Wat 860 and 935 MeV, have been measured using the double-arm time-of-flight spectrometer CORSET at the U400 cyclotron of the Flerov Laboratory of Nuclear Reactions (FLNR) at the Joint Institute for Nuclear Research (JINR), Dubna. Results: Enhancement in the yield of products with masses 200-215 u has been found for both reactions. The cross sections of the formation of trans-target fragments with masses around 208 u are found to be about 10 mu b at the Coulomb barrier energy and reach the level of 0.5 mb at the energy above the barrier for side-to-side collision. Conclusions: The enhanced yield of products with masses heavier than the target mass confirms the important role of the closed shells at Z = 82 and N = 82, 126 in the inverse quasifission process in low-energy damped collisions. The orientation effect caused by the strong deformation of colliding nuclei can result in a gain in the yield of heavy target-like fragments.