Partition of excitation energy in peripheral heavy-ion reactions

Generation and division of excitation energy in heavy-ion collisions studied by measuring charged-particle survival fractions

“…Evidence of such a dependence has been reported in refs. [6,8] and there are indications that also in heavy systems the partition of excitation energy depends on the direction of nucleon flow (see ref. [ 9 ] and references therein).…”

“…This effect had already been suggested by Siwek-Wilczynska et al [ 6 ], and later in refs. [7,8], on the grounds of the participant-spectator approximation underlying the optimum Q-value model of Siemens et al [ 5 ]. The basic ingredient of this mechanism is that only the transferred fragment and the nucleus that absorbs the transferred mass are participants in the reaction, whereas the rest of the donor nucleus is only a spectator and thus remains "cold" in the reaction.…”

Evidence for a nonequilibrated dinuclear system in dissipative collisions at 19 MeV/nucleon

“…In many cases, and not only at bombarding energies greater than 10 MeV/nucleon, the lack of equilibrium is accompanied by features which cannot be explained within the framework of the NEM. In particular, some recent experiments [6,[8][9][10][11][12][13][14] show a dependence of the energy partition on the net nucleon flow, which is not predicted by the nucleon exchange models. This dependence is at present a matter of debate and its evidence is controversial.…”

“…The first is expected to be more appropriate at small energy losses, and the second at large energy losses, when deformations are more developed. In order to verify, as in recent attempts [11][12][13]26], whether incoherent processes alone are able to explain the observed strong correlation with the net mass drift, a simple calculation was performed. It is based on a nucleon exchange mechanism in energy space Fission probabilities vs TKEL/Z^TOT for fragments of mass A^=i \20 and 100 produced in the present symmetric collision '"^Sn-h'^^Sn (diamonds) and in the previously studied '^MoH-'^Mo at 18.7 MeV/nucleon (squares), respectively.…”