[en] A lot of experimental data on nuclear fission has been being collected for the last 65 years, allowing theoreticians to confront their models with reality. The first part of this work is dedicated to the computation of fission barriers. We have extended the HF + BCS (Hartree Fock + Bandeen-Cooper-Schrieffer) method in order to include a new set of polynomials on which wave functions can be broken to, more accurately than on Hermite's polynomials in the 2 fragment configuration. The fission barriers of 26 heavy nuclei from Thorium-230 to Nobelium-256 have been assessed and compared to experimental data, it appears that differences are no greater than 1 MeV. We have discovered a neat correlation between the variation of the experimental fission lifetimes of even Fermium isotopes and the computed heights of second barriers. Moreover our model reproduces the hyper-deformed well of Thorium-230 with a good agreement on the well depth. The second part deals with the scission region. We have performed Hartree-Fock calculations in order to explore different ways of fragmentation. We have shown that the harmonic oscillator gives a valid description of such ways. In order to compute the mean value of J² in the fragments we have been driven to propose an adequate definition of that quantity consistent with the non-locality property of the J² operator. (A.C.)

[en] The workshop was devoted to the understanding of compound-nuclear reactions. Even though the concept of compound nucleus is rather old, further research is necessary in order to establish a comprehensive, quantitative picture of the processes involved in the formation and decay of a compound nucleus. Experts in nuclear theory, experiment and data evaluation were brought together. The improvements made in optical model calculations and in the description of the optical potential were illustrated. Several presentations considered nuclear structure information required for the description of compound-nuclear reactions such as level densities and gamma-ray strength functions. Recent neutron-induced measurements were discussed. Theoretical and experimental work on the surrogate reaction were presented. Various sessions were dedicated to fission experiments and modelling. Different reaction mechanisms associated with the formation and decay of compound nuclei were considered as for example nucleon-induced radiative capture, fusion, pre-equilibrium processes, cluster emission, etc. The presentations have been parted into 12 topics: 1) optical model calculations, 2) optical potential, 3) Statistical model and gamma-ray strength functions, 4) level densities, 5) neutron induced reactions, 6) surrogate reactions, 7) fission measurements, 8) fission modelling, 9) heavy ions and fusion reactions, 10) nuclear reaction mechanisms, 11) nuclear data and evaluations, and 12) nuclear astrophysics

[en] The Hauser-Feshbach (HF) model with width fluctuation correction needs to be modified when strongly coupled direct reaction channels exist. We perform cross section calculations for compound reactions which include strongly coupled channels (direct), based on the Kawai-Kerman-McVoy (KKM) theory. In KKM the cross sections are expressed in terms of channel matrix, which is given by the coupled-channels method. Numerical calculations are given for the ²³⁸U elastic scattering cross sections, and the elastic enhancement factor. It is shown that the compound elastic cross sections are affected by the direct channels when the coupling is strong. (authors)

[en] The fission barriers of twenty-six isotopes of Thorium, Uranium, Plutonium, Californium, Fermium and Nobelium have been microscopically calculated up to and beyond the second saddle point within a constrained Hartree-Fock plus pairing approach. The Skyrme density-dependent effective force in its SkM* parametrization -rather well suited to the description of fission barriers- has been used in the particle-hole channel, whereas the usual HF plus BCS formalism with either a seniority force or a delta force has been implemented to treat pairing correlations. The energy correction due to the rotational zero-point motion has been approximately taken into account and the effects of triaxial and reflection asymmetric deformations have been investigated. When known, the experimental fission barrier heights are reproduced within about 1-2MeV. (orig.)

[en] Within the Hartree-Fock-BCS and Highly Truncated Diagonalization microscopic approaches we have calculated the ground-state binding energies of axially-deformed odd-Z, even-N nuclei in the A ∼ 130 region and of the even-even daughter nuclei resulting from one-proton emission. The deduced Q_p values are in fair agreement with available experimental data.

[en] In this work we report on recent microscopic calculations of K-isomeric states of two-quasiparticle character in well-deformed rare-earth nuclei and actinide nuclei. In these calculations we employ a Skyrme energy-density functional together with a seniority residual interaction in the Hartree-Fock-BCS approximation with self-consistent blocking (SCB). The strength of the seniority interaction is calibrated in a consistent way: as some of us showed in Ref. [1] for rare-earth nuclei, the same strength can be obtained in a fit on moments of inertia of even-even nuclei and in a fit on odd-even mass staggering. The former fitting protocol is used for the actinide nuclei studied here. Once the seniority force was adjusted we calculated properties of various K-isomeric states without additional parameters. Overall we have obtained a rather good agreement with available data around ¹⁵⁴Nd and in the ²³⁴U - ²³⁶Pu region. We also found that an octupole deformation lowers the excitation energy of the K^π = 6^- isomer in ²³⁴U.

[en] The region of well-deformed rare-earth nuclei provides a valuable testing ground to assess both single-particle (s.p.) and pairing properties, the latter being of course partly contingent on the former. Calculations of even-even, odd-even and odd-odd nuclei have been performed within a standard self-consistent Skyrme-Hartree-Fock plus seniority force BCS approach (with self-consistent blocking and taking into account time-reversal breaking effects for odd isotopes). We emphasize here the study of the influence of pairing properties on some spectroscopic properties. To that effect, we chose a parametrization of the Skyrme interaction which has proven to provide reasonable s.p. properties in general and in particular in this region, namely the well established Skyrme SIII force. The neutron and proton parameters of the seniority force (only n-n and p-p correlations are considered here) have been fitted from 3-points odd-even mass differences (centered on odd nuclei) for 16 odd-N and 14 odd-Z rare-earth isotopes yielding r.m.s energy differences from the experimental data of 75 and 122 keV respectively, quantities which are of the same order as the standard deviation of the experimental values (averaging around 600 keV). With the so-defined Hamiltonian we have calculated for a wide sample of well-deformed even-even nuclei in this region, moments of inertia within the M(Q) Inglis-Belyaev approximate ATDHFB ansatz corrected as in for the so-called Thouless-Valatin self-consistency effects. The spectroscopy of band-heads of the seniority-one type (evaluated as it has been done previously for a few actinide nuclei) has also been yielded and compared with experimental data, particularly around the ¹⁷⁸Hf region. Finally spectroscopic quadrupole moments and magnetic dipole moments have been evaluated for some of the above considered odd-N and odd-Z nuclear states. This document is composed of an abstract and the slides of the presentation. (authors)

[en] We calculate the direct-semidirect (DSD) radiative proton capture cross section on ¹¹²Sn, ⁶³Cu, and ²⁰⁹Bi in the microscopic Hartree-Fock-BCS approach using the Skyrme interaction. Compared to the compound process, the DSD process becomes dominant in the proton capture reaction above ten and several MeV incident proton energies. We compare several particle-vibration coupling forms, which is sensitive to the semidirect cross section. (authors)

[en] Prompt fission neutrons and gamma-rays emitted by excited primary fission fragments are indirect probes to the nuclear configurations present near the scission point. By studying detailed characteristics of these quantities, it is shown that one can discriminate between various assumptions regarding the sharing of the free energy at scission among the two fragments. The case of low-energy neutron-induced fission on ²³⁵U is studied and interpreted in terms of fission modes

[en] A time-reversal symmetry breaking Skyrme–Hartree–Fock approach is applied to the calculations of single-particle states in odd-mass nuclei. As a first step of a more complete treatment, the pairing correlations are not taken into account. The effects on single-particle spectra of the time-odd Hartree–Fock fields resulting from the current and spin-vector densities are studied. The associated removal of the Kramers degeneracy is interpreted in terms of diamagnetic/paramagnetic types of polarization of the even-even core generated by the presence of an odd particle. (author)