Break-up fragments excitation and the freeze-out volume

We investigate, in microcanonical multifragmentation models, the influence of the amount of energy dissipated in break-up fragments excitation on freeze-out volume determination. Assuming a limiting temperature that decreases with nuclear mass, we obtain for the Xe+Sn at 32 MeV/nucleon reaction a freeze-out volume that is almost half the one deduced using a constant limiting temperature.

Figure 1

(Color online) Break-up charge distributions corresponding to the (230, 94) nuclear system with $E_{\mathrm{ex}}=5.3$ MeV/nucleon and 9$V_0$ (solid, dashed, and dotted lines) and 5.5$V_0$ (open circles). The amount of excitation energy absorbed by primary fragments is modified via the limiting temperature τ.

Figure 2

Average excitation energies of primary fragments obtained from the multifragmentation of the (230,94) nuclear system with $E_{\mathrm{ex}}=5.3$ MeV/nucleon and different freeze-out volumes and limiting temperatures.

Figure 3

(Color online) Break-up stage (upper panel) and asymptotic stage (lower panel) mean kinetic energy distributions as a function of charge obtained for the considered cases.

Figure 4

(Color online) Calculated asymptotic stage (histogram) and experimental (open symbols) charge distributions corresponding to Xe+Sn at 32 MeV/nucleon.

Figure 5

(Color online) Same as Fig. 4, but for distributions of multiplicity of number of intermediate mass fragments ($Z\ge 5$).

Figure 6

(Color online) Same as Fig. 4, but for distributions of fragment average kinetic energy as a function of charge.