Fast-fission reactions in collisions of four heavy systems (well below
the fusion extra-push energy threshold), for which Hinde and coworker
s had measured the prescission neutron multiplicities, have been analy
sed in terms of the deterministic dynamic model of Feldmeier coupled t
o a time-dependent statistical cascade calculation. In order to reprod
uce the measured prescission multiplicities and the observed (nearly s
ymmetric) mass divisions, the energy dissipation must be dramatically
changed with regard to the standard one-body dissipation: In the entra
nce channel, in the process of forming a composite system, the energy
dissipation must be reduced to at least half of the one-body dissipati
on strength (k(s)(in) less than or equal to 0.5), and in the exit chan
nel (from a mononucleus shape to scission) it must be increased to abo
ut 10 times that value (k(s)(out) approximate to 10).