Wojciech Satula

Competition between T = 0 and T = 1 pairing in proton-rich nuclei

Abstract A cranked mean-field model with two-body T = 1 and T = 0 pairing interactions is presented. Approximate projection onto good particle-number is enforced via an extended Lipkin-Nogami scheme. Our calculations suggest the simultaneous presence of both T = 0 and T = 1 pairing modes in N = Z nuclei. The transitions between different pairing phases are discussed as a function of neutron/proton excess, Tz, and rotational frequency, ħω. The additional binding energy due to the T = 0 np-pairing correlations, is suggested as a possible microscopic explanation of the Wigner energy term in even-even nuclei.

Structure of superdeformed states in AuRa nuclei

Abstract Energies of superdeformed states in nuclei around 192 Hg are calculated using the Strulinsky shell correction method with an average Woods-Saxon potential and a monopole pairing force. The influence of various terms in the model hamiltonian on the excitation energy of the superdeformed minimum is analysed. The systematics of calculated excitation energies of shape-isomeric minima and barrier heights in even-even HgRa nuclei are given together with predictions for one-quasiparticle band-head energies in odd-A Au, Hg, Tl, Pb and Bi nuclei. Possible occurrence of hyperdeformed states in very neutron-deficient PoRa isotopes is investigated. It is shown that the presence of these exotic configurations is strongly related to the magnitude of pairing correlations at strongly elongated shapes. Finally, the role played by reflection-asymmetric deformations at superdeformed shapes is discussed.

Competition between triaxial bands and highly deformed intruder bands around 180Os

Abstract Angular momentum alignment processes in nuclei around 180 Os are discussed within the deformed shell model using the Woods-Saxon potential and the monopole pairing interaction. The crossings between bands of different structures are analysed and predictions are made for the possible observation of highly deformed intruder bands. Predictions of Q o moments are presented for the highly deformed bands and tables of calculated deformations for 178–183 Os are given.

Microscopic Structure of Fundamental Excitations in N = Z Nuclei

An extended mean-field model is presented that describes states of different isospin in odd-odd and even-even nuclei. Excitation energies of the T = 1 states in even-even as well as T = 0 and T = 1 states in odd-odd N = Z nuclei are calculated. It is shown that the structure of these states can be determined in a consistent manner when both isoscalar and isovector pairing collectivity as well as isospin projection (treated here within the isocranking approximation) are taken into account. In particular, in odd-odd N = Z nuclei, the interplay between quasiparticle excitations (relevant for the case of T = 0 states) and isorotations (relevant for the case of T = 1 states) explains the near degeneracy of these states.

Spin-orbit and tensor mean-field effects on spin-orbit splitting including self-consistent core polarizations

A new strategy of fitting the coupling constants of the nuclear energy density functional is proposed, which shifts attention from ground-state bulk to single-particle properties. The latter are analyzed in terms of the bare single-particle energies and mass, shape, and spin core-polarization effects. Fit of the isoscalar spin-orbit and both isoscalar and isovector tensor coupling constants directly to the f{sub 5/2}-f{sub 7/2} spin-orbit splittings in {sup 40}Ca, {sup 56}Ni, and {sup 48}Ca is proposed as a practical realization of this new program. It is shown that this fit requires drastic changes in the isoscalar spin-orbit strength and the tensor coupling constants as compared to the commonly accepted values, but it considerably and systematically improves basic single-particle properties including spin-orbit splittings and magic-gap energies. Impact of these changes on nuclear binding energies is also discussed.

Rotations in Isospace: A Doorway to the Understanding of Neutron-Proton Superfluidity in N = Z Nuclei

The T = 2 excitations in even-even N = Z nuclei are calculated within the isospin cranked mean-field approach. The response of pairing correlations to rotation in isospace is investigated. Whereas the isovector pairing rather modestly modifies the single-particle moment of inertia in isospace, the isoscalar pairing strongly reduces its value. This reduction of the isomoments of inertia with respect to its rigid body value is a strong indicator of collective isoscalar pairing correlations. These results are further generalized yielding beautiful analogies between the role of isovector pairing for the case of spatial rotations and the role of isoscalar pairing for the case of isorotations.

Mean-field description of high-spin states

Recent high-spin observations reveal entirely new modes of collective rotational motion and the existence of novel symmetries and spontaneous symmetry breaking phenomena, uncovering hitherto unexploited coupling schemes of intrinsic and collective degrees of freedom. It continues to stimulate the theoretical progress in the field, which clearly turns towards a microscopic description based on self-consistent approaches using either an effective non-relativistic Hamiltonian or an effective relativistic Lagrangian. New coupling schemes call not only for symmetry unrestricted mean-field theories, but also for extensions going beyond the mean-field. The progress in the development of these theoretical methods is discussed in this review.

Isospin mixing in nuclei within the nuclear density functional theory.

We present the self-consistent, nonperturbative analysis of isospin mixing using the nuclear density functional approach and the rediagonalization of the Coulomb interaction in the good-isospin basis. The unphysical isospin violation on the mean-field level, caused by the neutron excess, is eliminated by the proposed method. We find a significant dependence of the magnitude of isospin breaking on the parametrization of the nuclear interaction. A rough correlation has been found between the isospin-mixing parameter and the difference of proton and neutron rms radii.

Blocking effects at super-deformed shape

Abstract The strongly reduced blocking effect in the supper-deformed HgPb region is investigated by means of the cranked Strutinsky pairing and deformations selfconsistent Lipkin-Nogami approach including both monopole and quadrupole pairing interaction. The simultaneous reduction of monopole and quadrupole pair correlations due to blocking has opposite effect on the dynamical moments of inertia. This provides an additional cancellation mechanism that levels out the difference between odd and even nuclei.

Microscopic Calculations of Isospin-Breaking Corrections to Superallowed Beta Decay

The superallowed β-decay rates that provide stringent constraints on physics beyond the standard model of particle physics are affected by nuclear structure effects through isospin-breaking corrections. The self-consistent isospin- and angular-momentum-projected nuclear density functional theory is used for the first time to compute those corrections for a number of Fermi transitions in nuclei from A=10 to A=74. The resulting leading element of the Cabibbo-Kobayashi-Maskawa matrix, |V(ud)|=0.97447(23), agrees well with the recent result of Towner and Hardy [Phys. Rev. C 77, 025501 (2008)].