Effects of the secondary decays on the isotopic thermometers

The sharp microcanonical multifragmentation model from [Al. H. Raduta and Ad. R. Raduta, Phys. Rev. C 55, 1344 (1997); Phys. Rev. C, in press] is employed for evaluating the nuclear caloric curve predictions of nine isotopic thermometers for three representative nuclei. Evaluations are performed for both primary decay and asymptotic stages. Effects of the secondary decays on the primary decay caloric curves are evidenced and discussed. In both cases a dispersive character of the isotopic caloric curves with increasing the source excitation energy is observed. A procedure of calibrating the isotopic thermometers on the microcanonical predictions for both primary decay and asymptotic stages is proposed. The resulting set of calibrating parameters for each thermometer is independent on the source size, on its excitation energy and, in the case of the primary decay, on the freeze-out radius assumption.Comment: 13 pages, 5 figures, Nuclear Physics A, in pres

Homogeneity and Size Effects on the Liquid-Gas Coexistence Curve

The effects of (in)homogeneity and size on the phase diagram of Lennard-Jones fluids are investigated. It is shown that standard multifragmentation scenarios (finite equilibrated systems with conserved center of mass position and momentum) are implying a strong radial inhomogeneity of the system strongly affecting the phase diagram. The homogeneity constraint is therefore necessary for finite systems in order to align to the ``meaning'' of infinite systems phase diagrams. In this respect, a method which deduces the equation of state of homogeneous finite systems from the one corresponding to bulk matter is designed. The resultant phase diagrams show a strong dependence on the system's size.Comment: 4 pages, 4 figure

Probing clustering in excited alpha-conjugate nuclei

15 pages, 6 figures, accepted in Physics Letters B; International audience; The fragmentation of quasi-projectiles from the nuclear reaction $^{40}$Ca+$^{12}$C at 25 MeV per nucleon bombarding energy was used to produce $\alpha$-emission sources. From a careful selection of these sources provided by a complete detection and from comparisons with models of sequential and simultaneous decays, evidence in favor of $\alpha$-particle clustering from excited $^{16}O$, $^{20}Ne$ and $^{24}Mg$ is reported

Evidence for α\alpha-particle condensation in nuclei from the Hoyle state deexcitation

The fragmentation of quasi-projectiles from the nuclear reaction $^{40}$Ca+$^{12}$C at 25 MeV/nucleon was used to produce excited states candidates to $\alpha$-particle condensation. Complete kinematic characterization of individual decay events, made possible by a high-granularity 4$\pi$ charged particle multi-detector, reveals that 7.5$\pm$4.0% of the particle decays of the Hoyle state correspond to direct decays in three equal-energy $\alpha$-particles.Comment: Phys. Lett. B, in pres

Thermodynamics of stellar matter: frustration, dishomogeneities and ensemble inequivalence

A paraîtreInternational audienc

Isospin dependent thermodynamics of fragmentation

The thermal and phase properties of a multifragmentation model that uses clusters as degrees of freedom are explored as a function of isospin. Good qualitative agreement is found with the phase diagram of asymmetric nuclear matter as established by different mean-field models. In particular, from the convexity properties of the nuclear entropy, we show that uncharged finite nuclei display first- and second-order liquid-gas-like phase transitions. Different quantities are examined to connect the thermal properties of the system to cluster observables. In particular, we show that fractionation is only a loose indication of phase coexistence. A simple analytical formula is proposed and tested to evaluate the symmetry (free) energy from the widths of isotopic distributions. Assuming that one may restore the isotopic composition of breakup fragments, it is found that some selected isotopic observables can allow one to quantitatively access the freeze-out symmetry energy in multifragmentation experiments

Nuclear Statistical Equilibrium Equation of State for Core Collapse

International audienceExtensive calculations of properties of supernova matter are presented, using the extended Nuclear Statistical Equilibrium model of Ref. [1] based on a statistical distribution of Wigner–Seitz cells modeled using realistic nuclear mass and level density tables, complemented with a non-relativistic Skyrme functional for unbound particles and beyond drip-line nuclei. Both thermodynamic quantities and matter composition are examined as a function of baryonic density, temperature, and proton fraction, within a large domain adapted for applications in supernova simulations. The results are also provided in the form of a table, with grid mesh and format compatible with the CompOSE platform [2] for direct use in supernova simulations. Detailed comparisons are also presented with other existing databases, all based on relativistic mean-field functionals, and the differences between the different models are outlined. We show that the strongest impact on the predictions is due to the different hypotheses used to define the cluster functional and its modifications due to the presence of a nuclear medium