LAUSR

A previous study of symmetric collisions of massive nuclei has shown that current models of multinucleon transfer (MNT) reactions do not adequately describe the transfer product yields. To gain further insight into this problem, we have measured the yields of MNT products in the interaction of 977 ($E/A=4.79$ MeV) and 1143 MeV ($E/A=5.60$ MeV) $^{204}\mathrm{Hg}$ with $^{208}\mathrm{Pb}$. We find that the yield of multinucleon transfer products are similar in these two reactions and are substantially lower than those observed in the reaction of 1257 MeV ($E/A=6.16$ MeV) $^{204}\mathrm{Hg}+^{198}\mathrm{Pt}$. We compare our measurements with the predictions of the GRAZING-F, dinuclear systems (DNS), and improved quantum molecular dynamics (ImQMD) models. For the observed isotopes of the elements Au, Hg, Tl, Pb, and Bi, the measured values of the MNT cross sections are orders of magnitude larger than the predicted values. Furthermore, the various models predict the formation of nuclides near the $N=126$ shell, which are not observed.