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}\mathrm{Sr}$${+}^{176}$Yb at an energy slightly above the Bass barrier ($E_{\text{c.m.}}/E_{\text{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.

• Received 6 December 2013
• Revised 9 January 2014

DOI:https://doi.org/10.1103/PhysRevC.89.014614