Ghoshal-like test of equilibration in near-Fermi-energy heavy-ion collisions

Calorimetric and coalescence techniques have been employed to probe equilibration for hot nuclei produced in heavy-ion collisions of 35 to 55 MeV/nucleon projectiles with medium mass targets. Entrance channel mass asymmetries and energies were selected so that very hot composite nuclei of similar mass and excitation would remain after early stage preequilibrium particle emission. Intercomparison of the properties and deexcitation patterns for these different systems provides evidence for the production of hot nuclei with decay patterns relatively independent of the specific entrance channel.

Figure 1

Time evolution of the double isotope ratio temperature, $T_{H\hspace{1em}\mathrm{He}}$, for the four different reactions. Key is as follows: 35 MeV/nucleon ${}^{64}\mathrm{Zn}+{}^{92}\mathrm{Mo}$ (red diamonds), 40 MeV/nucleon ${}^{40}\mathrm{Ar}+{}^{112}\mathrm{Sn}$ (orange triangles), 55 MeV/nucleon ${}^{27}\mathrm{Al}+{}^{124}\mathrm{Sn}$ (yellow circles), and 47 MeV/nucleon ${}^{64}\mathrm{Zn}+{}^{92}\mathrm{Mo}$ (blue squares).

Figure 2

Comparison of initial properties of the hot nuclei and deexcitation modes for the four different systems. (a) Masses of the deexciting hot nuclei; (b) excitation energies of the hot nuclei; (c) double isotope temperatures, $T_{H\hspace{1em}\mathrm{He}}$; (d)–(f) slope temperatures for n, p and t; (g)–(l) multiplicities of n, p, d, t, ${}^3\mathrm{He}$, and $\alpha$; (m)–(r) average kinetic energies of n, p, d, t, ${}^3\mathrm{He}$, and $\alpha$ in the hot nucleus frame. Solid points represent the data for the four different systems. Open squares show the results of gemini calculations [29]. Open triangles show the results of SMM calculations [30].