P.-H. Heenen

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.

Tensor part of the Skyrme energy density functional. II: Deformation properties of magic and semi-magic nuclei

We study systematically the impact of the time-even tensor terms of the Skyrme energy density functional, i.e., terms bilinear in the spin-current tensor density, on deformation properties of closed-shell nuclei corresponding to 20,28,40,50,82, and 126 neutron or proton shell closures. We compare results obtained with three different families of Skyrme parametrizations whose tensor terms have been adjusted on properties of spherical nuclei: (i) TIJ interactions proposed in the first article of this series [T. Lesinski et al., Phys. Rev. C 76, 014312 (2007)] that were constructed through a complete readjustment of the rest of the functional and (ii) parametrizations whose tensor terms have been added perturbatively to existing Skyrme interactions, with or without readjusting the spin-orbit coupling constant. We analyze in detail the mechanisms at play behind the impact of tensor terms on deformation properties and how studying the latter can help screen out unrealistic parametrizations. It is expected that findings of the present article are to a large extent independent of remaining deficiencies of the central and spin-orbit interactions and will be of great value for the construction of future, improved energy functionals.

Excitation energies and spins of the yrast superdeformed band inHg191

The excitation energies and spins of the levels in the yrast superdeformed band of {sup 191}Hg have been determined from two single-step {gamma} transitions and the quasicontinuum spectrum connecting the superdeformed and normal-deformed states. The results are compared with those from theoretical mean-field calculations with different interactions. A discussion of pairing in superdeformed states is also included.

Shape coexistence at the proton drip-line: First identification of excited states in Pb180

Excited states in the extremely neutron-deficient nucleus {sup 180}Pb have been identified for the first time using the JUROGAM II array in conjunction with the RITU recoil separator at the Accelerator Laboratory of the University of Jyvaeskylae. This study lies at the limit of what is presently achievable with in-beam spectroscopy, with an estimated cross section of only 10 nb for the {sup 92}Mo({sup 90}Zr,2n){sup 180}Pb reaction. A continuation of the trend observed in {sup 182}Pb and {sup 184}Pb is seen, where the prolate minimum continues to rise beyond the N=104 midshell with respect to the spherical ground state. Beyond-mean-field calculations are in reasonable correspondence with the trends deduced from experiment.

Configuration mixing of angular-momentum and particle-number projected triaxial HFB states using the Skyrme energy density functional

We present a method based on mean-field states generated by triaxial quadrupole constraints which are projected on particle number and angular momentum and mixed by the generator coordinate method on the quadrupole moment. This method is equivalent to a seven-dimensional GCM calculation, mixing all five degrees of freedom of the quadrupole operator and the gauge angles for protons and neutrons. A first application to Mg24 permits to analyze in detail the effects of triaxial deformations and of K-mixing.

Nuclear Structure at the Extremes; In‐beam γ‐ray Spectroscopy of 180Pb

For the first time, the excited states in the extremely neutron‐deficient nucleus 180Pb have been observed in an in‐beam γ‐ray measurement employing the recoil‐decay tagging technique. Deduced level energies follow the trend of prolate intruder band level energies derived from heavier lead isotopes and reflect the persistence of magicity of the closed Z = 82 proton shell when approaching the proton drip line.

Triaxial nuclear dynamics of Sr isotopes studied by the generator coordinate method

We present results obtained by the generator coordinate method (GCM) with HF+BCS wave functions as generating functions. We indicate how this method has to be generalized for the study of triaxial nuclear dynamics. We apply it to the light strontium isotopes. For neutron numbers intermediate between the spherical 88Sr and the very deformed (78Sr), the Sr isotopes are soft against γ deformations, exhibiting in the case of 80Sr and 82Sr spherical, oblate and triaxial minima nearly degenerate in energy. We show how the GCM permits to resolve this degeneracy and generates correlations which strongly influence one‐body observables like the mean square radii.

Rotational properties of {252, 253, 254} No

Abstract Rotational bands of 252,253,254No and the fission barriers of 254No at spin 0 ℏ and 20 ℏ are calculated with the Hartree–Fock–Bogolyubov theory and the Lipkin–Nogami approximate particle number projection. The SLy4 Skyrme force is used in the particle–hole channel. A zero-range force with and without density-dependence is used in the particle–particle channel. The experimental ground state deformation ( Q 20 =32.8 b) is reproduced as well as the increase of the dynamical moment of inertia with frequency both for 252No and 254No. The rotational band of 253No is also calculated. Fission barriers of 254No at spin 0 ℏ and 20 ℏ show the robustness of shell-corrections against rotation in these heavy nuclei.

Rotational properties of No-252,No-253,No-254: influence of pairing correlations

Abstract Rotational bands of 252,253,254No and the fission barriers of 254No at spin 0 ℏ and 20 ℏ are calculated with the Hartree–Fock–Bogolyubov theory and the Lipkin–Nogami approximate particle number projection. The SLy4 Skyrme force is used in the particle–hole channel. A zero-range force with and without density-dependence is used in the particle–particle channel. The experimental ground state deformation ( Q 20 =32.8 b) is reproduced as well as the increase of the dynamical moment of inertia with frequency both for 252No and 254No. The rotational band of 253No is also calculated. Fission barriers of 254No at spin 0 ℏ and 20 ℏ show the robustness of shell-corrections against rotation in these heavy nuclei.

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.