Reaction products from the system 136 Xe + 208 Pb at 136 Xe ions laboratory energies of 700, 870, and 1020 MeV were studied by two-body kinematics and by a catcher-foil activity analysis to explore the theoretically proposed suitability of such reaction as a means to produce neutron-rich nuclei in the neutron shell closure N = 126. Cross sections for products heavier than 208 Pb were measured and were found sensibly larger than new theoretical predictions. Transfers of up to 16 nucleons from Xe to Pb were observed.

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This work is a study of the influence of shell effects on the formation of binary fragments in damped collision. We have investigated binary reaction channels of the composite system with Z = 108 produced in the reaction 88 Sr+ 176 Yb at an energy slightly above the Bass barrier (E c.m. /E Bass = 1.03). Reaction products were detected by using the two-arm time-of-flight spectrometer CORSET at the K130 cyclotron of the Department of Physics, University of Jyväskylä. The mass-energy distribution of primary binary fragments has been measured. For targetlike fragments heavier than 190 u, which correspond to a mass transfer as large as twenty nucleons or more, an enhancement of the yields is observed. This striking result can be ascribed to the proton shells at Z = 28 and 82 and implies the persistence of the shell effects in the formation of reaction fragments even for large mass transfers.

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