Breakup Densities of Hot Nuclei

Breakup densities of hot ${}^{197}\mathrm{A}\mathrm{u}$-like residues have been deduced from the systematic trends of Coulomb parameters required to fit intermediate-mass-fragment kinetic-energy spectra. The results indicate emission from nuclei near normal nuclear density below an excitation energy $E^{*}/A\lesssim 2\mathrm{M}\mathrm{e}\mathrm{V}$, followed by a gradual decrease to a near-constant value of $\rho /{\rho }_0\sim 0.3$ for $E^{*}/A\gtrsim 5\mathrm{M}\mathrm{e}\mathrm{V}$. Temperatures derived from these data with a density-dependent Fermi-gas model yield a nuclear caloric curve that is generally consistent with those derived from isotope ratios.

Figure 1

Energy spectra at 43° and 137° for carbon fragments emitted from the $4.8\mathrm{G}\mathrm{e}\mathrm{V}/c$ ${}^3\mathrm{H}\mathrm{e}+{}^{197}\mathrm{A}\mathrm{u}$ reaction as a function of excitation energy. Symbols are as follows: $\langle E^{*}/A\rangle =3.4\mathrm{M}\mathrm{e}\mathrm{V}$ (●); 4.6 MeV (□); 5.7 MeV (△); 6.8 MeV (◇); 7.9 MeV (▼).

Figure 2

Top: Dependence of the average moving-source Coulomb parameter $\langle k_C\rangle$ as a function of excitation energy. Symbols are as follows: 200 MeV ${}^4\mathrm{H}\mathrm{e}$ (▪); ${}^{14}\mathrm{N}$ (▲); 4.8 GeV ${}^3\mathrm{H}\mathrm{e}$ (○). Bottom: Average density $\langle \rho /{\rho }_0\rangle$ as a function of $E^{*}/A$ derived from the $k_C$ values in the top panel.

Figure 3

First-order density-dependent Fermi-gas temperatures as a function of excitation energy. The dashed line is the normal-density Fermi-gas prediction, with $T=\sqrt{11.3(E^{*}/A)}\mathrm{M}\mathrm{e}\mathrm{V}$. Symbols are the same as in Fig. 2.

Figure 4

Corrected temperature versus excitation energy per nucleon for the data of Fig. 2. Circles show the density-corrected temperature points for the data. The solid and dashed lines show the Fermi-gas behavior for $K=8\mathrm{M}\mathrm{e}\mathrm{V}$ and $K=15.2\mathrm{M}\mathrm{e}\mathrm{V}$ with no density dependence.