  To investigate the two-body dissipation effects on the synthesis of
superheavy elements, we calculate low-energy collisions of the $N=50$ isotones
($^{82}$Ge, $^{84}$Se, $^{86}$Kr and $^{88}$Sr) on $^{208}$Pb using the
time-dependent density-matrix theory (TDDM). TDDM is an extension of the
time-dependent Hartree-Fock (TDHF) theory and can determine the time evolution
of one-body and two-body density matrices. Thus TDDM describes both one-body
and two-body dissipation of collective energies. It is shown that the two-body
dissipation may increase fusion cross sections and enhance the synthesis of
superheavy elements.
