J. Dudek

Critical frequency in nuclear chiral rotation

Self-consistent solutions for the so-called planar and chiral rotational bands in 132La are obtained for the first time within the Skyrme-Hartree-Fock cranking approach. It is suggested that the chiral rotation cannot exist below a certain critical frequency which under the approximations used is estimated as Plancks omega(crit) approximately 0.5-0.6 MeV. However, the exact values of Plancks omega(crit) may vary, to an extent, depending on the microscopic model used, in particular, through the pairing correlations and/or calculated equilibrium deformations. The existence of the critical frequency is explained in terms of a simple classical model of two gyroscopes coupled to a triaxial rigid body.

A comparative study of superdeformation in 146,147,148Gd. Possible manifestations of the pseudo-SU3 symmetry, octupole shape susceptibility and superdeformed deep-hole excitations

Abstract Two discrete superdeformed (SD) bands have been identified in the nucleus 147Gd and the twin-band mechanism studied by comparison with SD results for 146,148Gd. Theoretical interpretation in terms of nucleonic orbitals with the Woods-Saxon potential is consistent with the pseudo-spin symmetry picture and the octupole susceptibility mechanism predicted by theory.

Point symmetries in the Hartree-Fock approach. I. Densities, shapes, and currents

Three mutually perpendicular symmetry axes of the second order, inversion, and time reversal can be used to construct a double point group denoted by D2h(TD). Properties of this group are analyzed in relation to the symmetry and symmetry-breaking effects within the mean-field (Hartree-Fock) theories, both in even and odd fermion systems. We enumerate space symmetries of local one-body densities, and symmetries of electromagnetic moments, that appear when some or all of the D2h(TD) elements represent self-consistent mean-field symmetries.

Superdeformed bands in S-32 and neighboring nuclei predicted within the Hartree-Fock method

Superdeformed configurations in 32S, and in neighboring nuclei 33S, 31S, 33Cl, and 31P, are determined within the Hartree-Fock approach with the Skyrme interaction. Energies, angular momenta, quadrupole moments, particle-emission Q-values, and relative alignments and quadrupole moments are calculated for a number of superdeformed rotational bands in these nuclei. A new mechanism implying an existence of signature-separated rotational bands, distinct from the well-known signature-split bands, is discussed and associated with the time-odd channels of effective interactions.

NUCLEI WITH TETRAHEDRAL SYMMETRY

We discuss a point-group-theory based method of searching for new regions of nuclear stability. We illustrate the related strategy with realistic calculations employing the tetrahedral and the octahedral point groups. In particular, several nuclei in the Rare Earth region appear as excellent candidates to study the new mechanism.

SYMMETRIES IN THE INTRINSIC NUCLEAR FRAMES

Structure of symmetrization group and its influence on symmetries in the intrinsic frame for collective nuclear models is analysed.

Pairing correlations in the superdeformed rotational bands: The frequency-deformation scaling

Abstract Microscopic calculations overestimate the amount of angular momentum carried by the superdeformed rotational band in 152 Dy. This discrepancy between experiment and theory can be accounted for by the dynamic pairing correlations. Reasons for the particular importance of these correlations in fast rotating and strongly deformed nuclei are discussed.

Microscopic study of superdeformed rotational bands in 151Tb

Abstract Structure of eight experimentally known superdeformed bands in the nucleus 151Tb is analyzed using the results of the Hartree–Fock and Woods–Saxon cranking approaches. It is demonstrated that far going detailed similarities between the two approaches exist and predictions related to the structure of rotational bands calculated within the two models are nearly parallel. An interpretation scenario for the structure of the superdeformed bands is presented and predictions related to the exit spins are made. Small but systematic discrepancies between experiment and theory, analyzed in terms of the dynamical moments, J (2) , are shown to exist. These discrepancies can be parametrized in terms of a scaling factor f, such that modifications J (1),(2) →f J (1),(2) together with the implied scaling of the frequencies ω→f−1ω, correspond systematically better with the experimental data (f≃0.9) for both the Woods–Saxon and Hartree–Fock with Skyrme SkM★ interactions. The pairing correlations taken into account by using the particle-number-projection technique are shown to increase the disagreement. Sources of these systematic discrepancies are discussed — they are most likely related to the not yet optimal parametrization of the nuclear interactions used.

SHAPE EVOLUTION AT HIGH SPINS AND TEMPERATURES: NUCLEAR JACOBI AND POINCARE TRANSITIONS

We consider a realistic description of hot, fast rotating nuclei with the help of the macroscopic nuclear model, LSD, of Refs.1,2 We examine in particular a competition between Jacobi-type instabilities that preserve the left-right symmetry of nuclear systems and the Poincare-type ones that break this symmetry. It is shown that in exotic nuclei these two mechanisms should be considered together in order to reach the lowest-energy nuclear configurations. Results from our related experiments are discussed together with the examples of preliminary theoretical predictions.

INFLUENCE OF THE LEVEL DENSITY PARAMETRIZATION ON THE EFFECTIVE GDR WIDTH AT HIGH SPINS

Parameterizations of the nucleonic level densities are tested by computing the effective GDR strength-functions and GDR widths at high spins. Calculations are based on the thermal shape fluctuation method with the Lublin-Strasbourg Drop (LSD) model. Results for 106Sn, 147Eu, 176W, 194Hg are compared to the experimental data.