126 research outputs found
The Cranked Nilsson-Strutinsky versus the Spherical Shell Model: A Comparative Study of pf-Shell Nuclei
A comparative study is performed of a deformed mean field theory, represented
by the cranked Nilsson-Strutinsky (CNS) model, and the spherical shell model.
Energy spectra, occupation numbers, B(E2)-values, and spectroscopic quadrupole
moments in the light pf shell nuclei are calculated in the two models and
compared. The result is also compared to available experimental data which are
generally well described by the shell model. Although the Nilsson-Strutinsky
calculation does not include pairing, both the subshell occupation numbers and
quadrupole properties are found to be rather similar in the two models. It is
also shown that ``unpaired'' shell model calculations produce very similar
energies as the CNS at all spins. The role of the pairing energy in the
description of backbending and signature splitting in odd-mass nuclei is also
discussed.Comment: 14 pages, 20 figures, submitted to Phys.Rev.
Polarization Effects in Superdeformed Nuclei
A detailed theoretical investigation of polarization effects in superdeformed
nuclei is performed. In the pure harmonic oscillator potential it is shown that
when one particle (or hole) with the mass single-particle quadrupole moment
q_{nu} is added to a superdeformed core, the change of the electric quadrupole
moment can be parameterized as q_{eff}=e(bq_{nu}+a), and analytical expressions
are derived for the two parameters, and . Simple numerical expressions
for q_{eff}(q_\nu}) are obtained in the more realistic modified oscillator
model. It is also shown that quadrupole moments of nuclei with up to 10
particles removed from the superdeformed core of 152Dy can be well described by
simply subtracting effective quadrupole moments of the active single-particle
states from the quadrupole moment of the core. Tools are given for estimating
the quadrupole moment for possible configurations in the superdeformed A
150-region.Comment: 28 pages including 9 figure
Interpretation of the large-deformation high-spin bands in select A=158-168 nuclei
The high-spin rotational bands in Hf-168 and the triaxial bands in Lu nuclei are analyzed using the configuration-constrained cranked Nilsson-Strutinsky (CNS) model. Special attention is given to the up-sloping extruder orbitals. The relative alignment between the bands which appear to correspond to triaxial shape is also considered, including the yrast ultrahigh-spin band in Er-158. This comparison suggests that the latter band is formed from rotation around the intermediate axis. In addition, the standard approximations of the CNS approach are investigated, indicating that the errors which are introduced by the neglect of off-shell matrix elements and the cutoff at nine oscillator shells (N-max = 8) are essentially negligible compared to other uncertainties. On the other hand, the full inclusion of the hexadecapole degree of freedom is more significant; for example it leads to a decrease of the total energy of similar to 500 keV in the triaxial superdeformed (TSD) region of Hf-168
Triaxiality in 48Cr
Rotational behavior inducing triaxiality is discussed for 48Cr in the cranked
Nilsson-Strutinsky (CNS) model, as well as in the spherical shell model. It is
shown that the low-spin region up to about I=8, has a prolate well-deformed
shape. At higher spins the shape is triaxial with a "negative-gamma"
deformation, that is, with rotation around the classically forbidden
intermediate axis. By comparing calculated B(E2)-values and spectroscopic
quadrupole moments in the CNS with spherical shell model results and
experimental data, the triaxial rotation around the intermediate axis is
confirmed.Comment: 9 pages, including 6 figures; submitted to Physics Letters
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