15,595 research outputs found
Theoretical study of the decay-out spin of superdeformed bands in the Dy and Hg regions
Decay of the superdeformed bands have been studied mainly concentrating upon
the decay-out spin, which is sensitive to the tunneling probability between the
super- and normal-deformed wells. Although the basic features are well
understood by the calculations, it is difficult to precisely reproduce the
decay-out spins in some cases. Comparison of the systematic calculations with
experimental data reveals that values of the calculated decay-out spins scatter
more broadly around the average value in both the 150 and 190
regions, which reflects the variety of calculated tunneling probability in each
band.Comment: 6 pages 4 figures (30 PS files). To appear in Proc. of NS2000
(Nuclear Structure 2000) conf., at MSU, 15-19 Aug., 200
Efficient Method for Quantum Number Projection and Its Application to Tetrahedral Nuclear States
We have developed an efficient method for quantum number projection from most
general HFB type mean-field states, where all the symmetries like axial
symmetry, number conservation, parity and time-reversal invariance are broken.
Applying the method, we have microscopically calculated, for the first time,
the energy spectra based on the exotic tetrahedral deformation in
Zr. The nice low-lying rotational spectra, which have all
characteristic features of the molecular tetrahedral rotor, are obtained for
large tetrahedral deformation, \alpha_{32} \gtsim 0.25, while the spectra are
of transitional nature between vibrational and rotational with rather high
excitation energies for Comment: Trivial mistakes are correcte
On the Response Function Technique for Calculating the Random-Phase Approximation Correlation Energy
We develop a scheme to exactly evaluate the correlation energy in the
random-phase approximation, based on linear response theory. It is demonstrated
that our formula is completely equivalent to a contour integral representation
recently proposed by Donau et al. being numerically more efficient for
realistic calculations. Numerical examples are presented for pairing
correlations in rapidly rotating nuclei.Comment: 4 pages, 4 figure
High-K Precession modes: Axially symmetric limit of wobbling motion
The rotational band built on the high-K multi-quasiparticle state can be
interpreted as a multi-phonon band of the precession mode, which represents the
precessional rotation about the axis perpendicular to the direction of the
intrinsic angular momentum. By using the axially symmetric limit of the
random-phase-approximation (RPA) formalism developed for the nuclear wobbling
motion, we study the properties of the precession modes in W; the
excitation energies, B(E2) and B(M1) values. We show that the excitations of
such a specific type of rotation can be well described by the RPA formalism,
which gives a new insight to understand the wobbling motion in the triaxial
superdeformed nuclei from a microscopic view point.Comment: 14 pages, 8 figures (Spelling of the authors name was wrong at the
first upload, so it is corrected
Simple model for decay of superdeformed nuclei
Recent theoretical investigations of the decay mechanism out of a
superdeformed nuclear band have yielded qualitatively different results,
depending on the relative values of the relevant decay widths. We present a
simple two-level model for the dynamics of the tunneling between the
superdeformed and normal-deformed bands, which treats decay and tunneling
processes on an equal footing. The previous theoretical results are shown to
correspond to coherent and incoherent limits of the full tunneling dynamics.
Our model accounts for experimental data in both the A~150 mass region, where
the tunneling dynamics is coherent, and in the A~190 mass region, where the
tunneling dynamics is incoherent.Comment: 4 page
Spreading Width for Decay out of a Superdeformed Band
The attenuation factor F responsible for the decay out of a superdeformed
(SD) band is calculated with the help of a statistical model. This factor is
given by 1/F = (1 + Gamma(down) / Gamma(S)). Here, Gamma(S) is the width for
the collective E2 transition within the superdeformed band, and Gamma(down) is
the spreading width which describes the mixing between a state in the SD band
and the normally deformed (ND) states of equal spin. The attenuation factor F
is independent of the statistical E1 decay widths Gamma(N) of the ND states
provided that the Gamma(N) are much larger than both Gamma(down) and Gamma(S).
This condition is generically met. Previously measured values of F are used to
determine Gamma(down).Comment: Submitted to Physical Review Letter
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