8,615 research outputs found
How large is the spreading width of a superdeformed band?
Recent models of the decay out of superdeformed bands can broadly be divided
into two categories. One approach is based on the similarity between the
tunneling process involved in the decay and that involved in the fusion of
heavy ions, and builds on the formalism of nuclear reaction theory. The other
arises from an analogy between the superdeformed decay and transport between
coupled quantum dots. These models suggest conflicting values for the spreading
width of the decaying superdeformed states. In this paper, the decay of
superdeformed bands in the five even-even nuclei in which the SD excitation
energies have been determined experimentally is considered in the framework of
both approaches, and the significance of the difference in the resulting
spreading widths is considered. The results of the two models are also compared
to tunneling widths estimated from previous barrier height predictions and a
parabolic approximation to the barrier shape
Matrix Elements of Random Operators and Discrete Symmetry Breaking in Nuclei
It is shown that several effects are responsible for deviations of the
intensity distributions from the Porter-Thomas law. Among these are genuine
symmetry breaking, such as isospin; the nature of the transition operator;
truncation of the Hilbert space in shell model calculations and missing
transitionsComment: 8 pages, 3 figure
Geometry of Borromean Halo Nuclei
We discuss the geometry of the highly quantal nuclear three-body systems
composed of a core plus two loosely bound particles. These Borromean nuclei
have no single bound two-body subsystem. Correlation plays a prominent role.
From consideration of the value extracted from electromagnetic
dissociation, in conjunction with HBT-type analysis of the two valence-halo
particles correlation, we show that an estimate of the over-all geometry can be
deduced. In particular we find that the opening angle between the two neutrons
in He and Li are, respectively, and . These angles are
reduced by about 12% to and
if the laser spectroscopy values of the rms charge
radii are used to obtain the rms distance between the cores and the center of
mass of the two neutrons. The opening angle in the case of Li is more
than 20% larger than recently reported by Nakamura \cite{Nak06}. The analysis
is extended to Be and the two-proton Borromean nucleus Ne where
complete data is still not available. Using available experimental data and
recent theoretical calculations we find,
and , respectively.Comment: 5 pages, one figure, version to appear in PRC, Rapid Communication
- …