We report on a systematics of fusion cross section data at energies above the reaction threshold to those of disappearance of fusion process. By an appropriate scaling of both cross sections and ...energy, a fusion excitation function common to all the data points is established. A universal description of the fusion excitation function relying on basic nuclear concepts is proposed and its dependence on the reaction cross section used for the cross section normalization is discussed.
Within a liquid drop model the energy of the12C,16O,20Ne,24Mg and32S 4n-nuclei has been calculated within different configurations of α-molecules : linear chain, triangle, square, tetrahedron, ...pentagon, trigonal bipyramid, square pyramid, hexagon, octahedron, octagon and cube. The potential barriers governing the decay and entrance channels via α emission or absorption as well as the potential barriers of other possible binary and ternary reactions have been compared. The rms radii of the linear chains do not correspond to the experimental rms radii of the ground states. The binding energies of the three-dimensional molecules at the nascent point of the fragments are higher than the ones of the planar configurations. The A-4 daughter plus α particle configurations have always the lowest potential energy.
Presented is a universal description of the generalized fusion excitation function which indicates that the fusion reaction mechanism should vanish at center-of-mass energy per nucleon of about 13 ...MeV/nucleon independently of the specific heavy-ion reaction system. Placing reliance on this result and comforted by semiclassical transport model simulations we suggest that the proposed persistence of the incomplete fusion cross sections in the measurement of the 14N induced reactions on heavy targets at beam energies between 100A and 155A MeV should be attributed to a geometrical participant-spectator-like reaction mechanism.
The 4π array INDRA was used to detect nearly all charged products emitted in Ar + Ni collisions between 52 and 95 MeV/u. The charge, mass and excitation energy
E
∗
of the quasi-projectiles have been ...reconstructed event by event. Excitation energies up to 25 MeV per nucleon are reached. Apparent temperatures obtained from several double isotopic yield ratios
Tr
0 show different dependences upon
E
∗
.
T
6
Li
7
Li
3
Heα
0 yields the highest values, as well as the high energy slopes
Ts of the kinetic energy spectra. Two statistical models, sequential evaporation and gas in complete equilibrium, taking into account side feeding and discrete excited states population, show that the data can be explained by a steady increase of the initial temperature with excitation energy without evidence for a liquid-gas phase transition.
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