Comparing observational abundance features with nucleosynthesis predictions of stellar evolution or explosion simulations, we can scrutinize two aspects: (a) the conditions in the astrophysical production site and (b) the quality of the nuclear physics input utilized. We test the abundance features of r-process nucleosynthesis calculations for the dynamical ejecta of neutron star merger simulations based on three different nuclear mass models: The Finite Range Droplet Model, the (quenched version of the) Extended Thomas Fermi Model with Strutinsky Integral, and the Hartree-Fock-Bogoliubov mass model. We make use of corresponding fission barrier heights and compare the impact of four different fission fragment distribution models on the final r-process abundance distribution. In particular, we explore the abundance distribution in the second r-process peak and the rare-earth sub-peak as a function of mass models and fission fragment distributions, as well as the origin of a shift in the third r-process peak position. The latter has been noticed in a number of merger nucleosynthesis predictions. We show that the shift occurs during the r-process freeze-out when neutron captures and β-decays compete and an (n,γ)-(γ,n) equilibrium is no longer maintained. During this phase neutrons originate mainly from fission of material above A = 240. We also investigate the role of β-decay half-lives from recent theoretical advances, which lead either to a smaller amount of fissioning nuclei during freeze-out or a faster (and thus earlier) release of fission neutrons, which can (partially) prevent this shift and has an impact on the second and rare-earth peak as well.

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A new experimental approach is introduced to investigate the relaxation of the nuclear deformation degrees of freedom. Highly excited fissioning systems with compact shapes and low angular momenta are produced in peripheral relativistic heavy-ion collisions. Both fission fragments are identified in atomic number. Fission cross sections and fission-fragment element distributions are determined as a function of the fissioning element. From the comparison of these new observables with a nuclear-reaction code a value for the transient time is deduced. Introduction.-The process of equilibration of a highly excited nucleus in all its degrees of freedom is not yet well understood. A dynamical description of the equilibration process in terms of a purely microscopic theory is not possible to the present day due to the large number of degrees of freedom involved. For this reason, most of the current theoretical models are based on transport theories [1], where one distinguishes between collective and intrinsic degrees of freedom. The latter are not considered in detail but in an average sense as a heat bath. The transfer of excitation energy between collective and intrinsic degrees of freedom is denominated dissipation and quantified by the dissipation strength β, which may depend on excitation energy and deformation. PACSOne of the most intensively investigated nuclear collective motions is the fission process. In the frame of a transport theory, fission is the result of the evolution of the collective fission coordinates under the interaction with the heat bath and an external driving force given by the available phase space. This evolution can be obtained by solving the Langevin equation or its integral form, the Fokker-Planck equation (FPE) [2]. Already in 1940, Kramers [3] described the nuclear fission process within a transport theory and derived the stationary solution of the corresponding FPE. Later, by solving numerically the time-dependent FPE, Grangé et al. [4] investigated the transient effects that arise from the relaxation of the collective degrees of freedom. Their results showed that it takes a so-called transient time τ trans , until the fission width reaches 90% of its stationary value.The most frequently applied tools to measure nuclear times are the neutron clock [5] and the gamma clock [6]. They have yielded the majority of the available information on the time a heavy nuclear system needs to cross the scission point. However, the mean scission time is an integral value, including the transient time, the inverse of the stationary decay rate (the statistical decay time) and an additional dynamic saddle-to scission time. Thus it does not give direct access to the transient time that is connected to the equilibration process of the

We present an extensive overview of production cross sections and kinetic energies for the complete set of nuclides formed in the spallation of 136 Xe by protons at the incident energy of 1 GeV per nucleon. The measurement was performed in inverse kinematics at the GSI fragment separator. Slightly below the BusinaroGallone point, 136 Xe is the stable nuclide with the largest neutron excess. The kinematic data and cross sections collected in this work for the full nuclide production are a general benchmark for modeling the spallation process in a neutron-rich nuclear system, where fission is characterized by predominantly mass-asymmetric splits.

The production of light and intermediate-mass nuclides formed in the reaction 1 H + 238 U at 1 GeV was measured at the Fragment Separator at GSI, Darmstadt. The experiment was performed in inverse kinematics, by shooting a 1 A GeV 238 U beam on a thin liquid-hydrogen target. A total of 254 isotopes of all elements in the range 7 Z 37 were unambiguously identified, and the velocity distributions of the produced nuclides were determined with high precision. The results show that the nuclides are produced in a very asymmetric binary decay of heavy nuclei originating from the spallation of uranium. All the features of the produced nuclides merge with the characteristics of the fission products as their mass increases.

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Abstract.Coulomb breakup of unstable neutron rich nuclei 29,30 Na around the 'island of inversion' has been studied at energy around 434 MeV/nucleon and 409 MeV/nucleon respectively. Four momentum vectors of fragments, decay neutron from excited projectile and γ-rays emitted from excited fragments after Coulomb breakup are measured in coincidence. For these nuclei, the low-lying dipole strength above one neutron threshold can be explained by direct breakup model. The analysis for Coulomb breakup of 29,30 Na shows that large amount of the cross section yields the 28 Na, 29 Na core in ground state. The predominant ground-state configuration of 29,30 Na is found to be 28 Na(g.s) ⊗ ν s 1/2 and 29 Na(g.s) ⊗ ν s 1/2 , respectively.