No abstract available

[en] While the shell model is the most fundamental of nuclear structure models, states in light nuclei also have been described successfully in terms of clusters. Indeed, Wildemuth and Tang have shown a correspondence between the cluster and shell models, the clusters arising naturally as correlations out of the shell model Hamiltonian. For light nuclei, the cluster model reduces the many-body problem to a few-body one, with interactions occurring between the clusters. These interactions involve particle exchanges, since the nucleons may still be considered somewhat freely moving, with their motion not strictly confined to the clusters themselves. Such is the relation of the cluster model to the shell model. For a realistic shell model then, one may expect some evidence of clustering in the wave functions for those systems in which the cluster model is valid. The results obtained using the multi-ℎωshell model wave functions are closer in agreement with experiment than the results obtained using the 0ℎωwave functions. Yet in all cases, that level of agreement is not good, with the calculations underpredicting the measured values by at least a factor of two. This indicates that the shell model wave functions do not exhibit clustering behavior, which is expected to manifest itself at small momentum transfer. The exception is the transition to the 7^-/2 state in ⁷Li, for which the value obtained from the γ-decay width is in agreement with the value obtained from the MK3W and (0 + 2 + 4)ℎωshell model calculations

[en] The results of the spectroscopic electric quadrupole moment measurements of the odd-odd ²²Na nuclei are presented. The measurements were performed by the high resolution laser fluorescence method in the parallel atomic beam. The sign and the value of the quadrupole moment Q_S = +0,134(17) barns and the static quadrupole deformation parameter β₂=0,31(4) were determined. These values of Q_S and β₂ are lower than ones determined from the half-lives of the ²²Na rotational levels. (author)

[en] Previous determinations of the level density parameters, a, as derived from analyses of resonance parameter data, were carried out on the basis of the Gilbert-Cameron theoretical relation for the spin dispersion parameter, σ. However, other different theoretical expressions for σ have been derived previously on the basis of various nuclear models, such as the Fermi gas model, the unified Bohr-Mottelson model with and without inclusion of nucleon pairing correlations, and the Hartree-Fock model. The different expressions for σ would impact the derivation of the a parameter. Because of these considerations, a new examination of the level density parameter, devoid of a reliance on a theoretical expression for σ, is of great importance in various computations in the fields of reactor physics, astrophysics, and spallation neutrons. Here, the spin dispersion parameter of the level density formula, σ, as determined from the spin dependent level spacings of neutron resonances, is compared with theoretical expressions and found to be in agreement with the results of Ericson. On the basis of the present results, the level density parameters, a, for a few nuclides were then derived and found to be lower than previous determinations by about 20%. The impact of the present findings on the LAHET calculations of neutron yields from thick targets of W is discussed

[en] A recent interpretation of the caloric curve based on the expansion of the abraded spectator nuclear is re-analysed in the framework of the Time Dependent Hartree Fock (TDHF) evolution. It is shown that the TDHF dynamics can not be reduced to a single monopolar collective motion at moderate energy. The inclusion of other important collective degrees of freedom may lead to the dynamical creation of hollow structure. Then, low density regions could be locally reached after a long time by the creation of these exotic density profiles. The TDHF simulations do not confirm conclusions made when using an monopolar isentropic expansion. In particular the systematic of the minimum density reached during the expansion (the so-called turning points) appears to be different. (author)

No abstract available

[en] The report describes findings and conclusions of the 1st Research Coordination Meeting on Nuclear Model Parameter Testing for Nuclear Data Evaluation (Reference Input Parameter Library: Phase II). In particular, a critical review of the RIPL Starter File was performed, and a detailed scope and workplan of the RIPL-II project were prepared. In an appendix are included the extended abstracts of four technical papers presented at the meeting. A separate abstract was prepared for each paper

No abstract available

[en] The binding energies and root mean square radii obtained from the Integro-Differential Equation Approach (IDEA) and from the Weight Function Approximation (WFA) of the IDEA for an even number of bosons and for ¹²C, ¹⁶O and ⁴⁰Ca are compared to those recently obtained by the Variational Monte Carlo, Fermi Hypernetted Chain and Coupled Cluster expansion method with model potentials. The IDEA provides numbers very similar to those obtained by other methods although it takes only two-body correlations into account. The analytical expression of the wave function for the WFA is given for bosons in ground state when the interaction pair is outside the potential range. Due to its simple structure, the equations of the IDEA can easily be extended to realistic interaction for nuclei like it has already been done for the tri-nucleon and the ⁴He. (authors)

[en] Octupole correlations have been investigated within the Generator Coordinate Method based upon Hartree-Fock plus BCS wavefunctions. GCM states corresponding to the q₃₀ and q₃₂ modes have been built up to describe the SD excited bands which have been recently observed as negative parity bands. (authors)