NEUTRON CLOCK AS A FRICTION-METER

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).