S. J. Krieger

Self-consistent study of triaxial deformations: Application to the isotopes of Kr, Sr, Zr and Mo

Abstract Self-consistent mean-field calculations of deformation energy surfaces have been performed for more than 30 exotic isotopes of the Kr, Sr, Zr and Mo elements. Our calculations extend to the proton drip line. We investigate the triaxial stability of the deformed ground states in the deformation regions N ≈ 38 and N ≈ 60. The results are in good agreement with the observed trends.

An improved pairing interaction for mean field calculations using skyrme potentials

Abstract A zero-range interaction is proposed to calculate nuclear pairing at the Fermi surface. The results of Skyrme calculations using the zero range pairing interaction are compared with those using the constant G model for the pairing, as well as with those of a finite-range calculation. Particular attention is paid to the region of superdeformation and fission.

Superdeformation and shape isomerism at zero spin

Abstract Microscopic Hartree-Fock plus BCS calculations in three-dimensional coordinate space are performed to obtain potential energy surfaces in order to analyse shape isomerism in mass regions other than the well-documented fission isomers in the actinides. Many isotopes of platinum, mercury and osmium exhibit a second minimum with a large deformation and are thus candidates for shape isomerism. The same feature also occurs around the 68 Ni nucleus. The most promising candidates for experimental verification are delineated.

Quadrupole collective correlations and the depopulation of the superdeformed bands in mercury

Abstract Fully self-consistent generator coordinate method calculations have been performed on a basis of quadrupole constrained Hartree-Fock plus BCS wave functions for the five even mercury isotopes 190–198 Hg. The gcm results support conclusions drawn from previous HF + BCS calculations. The predicted evolution of superdeformed band head (shape isomer) properties as a function of the neutron number is consistent with the data. Using calculated transition matrix elements, we evaluate in-band versus out-of-band quadrupole decay and explain the sudden termination of the super-deformed band.

Super-deformation and shape isomerism: Mapping the isthmus☆

Abstract An isthmus of shape isomerism is mapped in the region of recently discovered super-deformation by computing well depths and excitation energies for 148 nuclei in fully microscopic, HF-BCS calculations. In all instances in which super deformed isomers have been experimentally observed, our calculations have predicted well deformed second minima with excitation energies and rigid body moments of inertia consistent with the data. Predictions for additional isomers are inferred from the present work.

From ground state to scission: The spinning life of 20Ne

Abstract We solve the cranked Hartree-Fock equations for the nucleus 20 Ne. We follow the yrast line from the ground state to the point where the nucleus fissions. We identify the several configurations which form the yrast line and we also study some excited particle-hole configurations. Quantum effects strongly increase the limiting angular momentum value in comparison with classical estimates. We briefly investigate temperature effects by calculating one isotherm.

GCM calculation of the E2 decay lifetimes of shape isomers

Abstract We apply the generator coordinate method (GCM) in a fully microscopic calculation of the E2 decay lifetime of the isomeric states of 238 U, 230 Thand 232 Th. The basis states have been generated by constrained HFBCS calculations with the potential SkM∗. Triaxial quadrupole deformations have been included. Comparison is made with experiment in the case of 238 U and experimenters are urged to search for the predicted decays in the thorium isotopes.

Microscopic Description of Superdeformation at Low Spin

Nuclear Hartree-Fock (HF)+BCS calculations have led to predictions of shape iso-merism in isotopes of Pt, Hg and Os nucleil. These have been confirmed through the observation of superdeformed rotational bands in190,…,194 Hg. Encouraged by these measurements and similar observations in 194Pb, we have extended these calculations to a wide range of contiguous nuclei. These HF results have been employed in a Generator Coordinate Method (GCM) calculation utilizing the quadrupole deformation as the generating variable2. The resulting spectra confirm the conclusions drawn from the HF results and agree with experiments.

Shape Isomers: Mean‐Field Description and Beyond

Nuclear Hartree-Fock (HF) + BCS calculations have led to predictions of shape isomerism in isotopes of Pt, Hg and Os nuclei. These have been confirmed through the observation of superdeformed rotational bands in {sup 190,{hor ellipsis},194}Hg. Encouraged by these measurements and similar observations in {sup 194}Pb, we have extended these calculations to a wide range of contiguous nuclei. These HF results, for {sup 192,194}Pt, {sup 190,{hor ellipsis},198}Hg and {sup 194}Pb, have been employed in a Generator Coordinate Method (GCM) calculation utilizing the quadrupole deformation as the generating variable. The resulting spectra confirm the conclusions drawn from the HF results and agree with those experiments which have been performed. Adding a phenomenological assumption for the moments of inertia of our GCM states, we can construct the radiative transitions within and out of the superdeformed band. The results are in good agreement with the observed de-population of the superdeformed band built upon the shape isomer both in minimum angular momentum and in rapidity of de-population. Inferences for the existence of shape isomers will be drawn. 19 refs., 4 figs.