213 research outputs found
Dipole resonances in light neutron-rich nuclei studied with time-dependent calculations of antisymmetrized molecular dynamics
In order to study isovector dipole response of neutron-rich nuclei, we have
applied a time-dependent method of antisymmetrized molecular dynamics. The
dipole resonances in Be, B and C isotopes have been investigated. In Be,
B, C, collective modes of the vibration between a core and
valence neutrons cause soft resonances at the excitation energy MeV
below the giant dipole resonance(GDR). In C, we found that a remarkable
peak at MeV corresponds to coherent motion of four valence neutrons
against a C core, while the GDR arises from the core vibration in the
MeV region. In B and C, the dipole strengths in the low
energy region decline compared with those in B and C. We also
discuss the energy weighted sum rule for the transitions.Comment: 12 figures, submitted to Phys. Rev.
Deformations in N=14 isotones
Systematic analysis of deformations in neutron-rich N=14 isotones was done
based on the method of antisymmetrized molecular dynamics. The property of the
shape coexistence in Si, which is known to have the oblate ground state
and the prolate excited states, was successfully described. The results suggest
that the shape coexistence may occur also in neutron-rich N=14 nuclei as well
as Si. It was found that the oblate neutron shapes are favored because
of the spin-orbit force in most of N=14 isotones. moments and
transition strengths in the neutron-rich nuclei were discussed in relation to
the intrinsic deformations, and a possible difference between the proton and
neutron deformations in Ne was proposed.Comment: 13 pages, 7 figures, sumitted to Phys.Rev.
Structure of excited states of Be-11 studied with Antisymmetrized Molecular Dynamics
The structures of the ground and excited states of Be-11 were studied with a
microscopic method of antisymmetrized molecular dynamics. The theoretical
results reproduce the abnormal parity of the ground state and predict various
kinds of excited states. We suggest a new negative-parity band with a
well-developed clustering structure which reaches high-spin states. Focusing on
a clustering structure, we investigated structure of the ground and
excited states. We point out that molecular orbits play important roles for the
intruder ground state and the low-lying states. The features of
the breaking of clusters were also studied with the help of data for
Gamow-Teller transitions.Comment: 24 pages, 7 figures, to be submitted to Phys.Rev.
Structure of Excited States of 10Be studied with Antisymmetrized Molecular Dynamics
We study structure of excited states of 10Be with the method of variation
after spin parity projection in the framework of antisymmetrized molecular
dynamics. Present calculations describe many excited states and reproduce the
experimental data of E2 and E1 transitions and the new data of the
transition strength successfully. We make systematic discussions on the
molecule-like structures of light unstable nuclei and the important role of the
valence neutrons based on the results obtained with the framework which is free
from such model assumptions as the existence of inert cores and clusters.Comment: 15 pages, RevTex, seven postscript figures (using epsf.sty
Exotic clusters in the excited states of Be-12, Be-14 and B-15
The excited states of Be-12, Be-14 and B-15 were studied by an
antisymmetrized molecular dynamics method. The theoretical results reproduced
the energy levels of recently measured excited states of Be-12, and also
predicted rotational bands with innovative clustering structures in Be-12,
Be-14 and B-15. Clustering states with new exotic clusters (He-6, He-8 and
Li-9) were theoretically suggested. One new aspect in very neutron-rich nuclei
is a 6-nucleon correlation among 4 neutrons and 2 protons, which plays an
important role in the formation of He-6 clusters during clustering: 8He + 6He
of Be-14 and 9Li+6He of B-15.Comment: 8 pages, 3 figures. submitted to Phys.Rev.
4He decay of excited states in 14C
A study of the 7Li(9Be,4He 10Be)2H reaction at E{beam}=70 MeV has been
performed using resonant particle spectroscopy techniques and provides the
first measurements of alpha-decaying states in 14C. Excited states are observed
at 14.7, 15.5, 16.4, 18.5, 19.8, 20.6, 21.4, 22.4 and 24.0 MeV. The
experimental technique was able to resolve decays to the various particle bound
states in 10Be, and provides evidence for the preferential decay of the high
energy excited states into states in 10Be at ~6 MeV. The decay processes are
used to indicate the possible cluster structure of the 14C excited states.Comment: accepted for publication in PR
Occupation probability of harmonic-oscillator quanta for microscopic cluster-model wave functions
We present a new and simple method of calculating the occupation probability
of the number of total harmonic-oscillator quanta for a microscopic
cluster-model wave function. Examples of applications are given to the recent
calculations including -model for He, -model for
Li, and -model for Be as well as the classical
calculations of -model for Li and -model
for C. The analysis is found to be useful for quantifying the amount of
excitations across the major shell as well as the degree of clustering. The
origin of the antistretching effect is discussed.Comment: 9 page
An Improved Quantum Molecular Dynamics Model and its Applications to Fusion Reaction near Barrier
An improved Quantum Molecular Dynamics model is proposed. By using this
model, the properties of ground state of nuclei from Li to Pb can
be described very well with one set of parameters. The fusion reactions for
Ca+Zr, Ca+Zr and Ca+Zr at energy near
barrier are studied by this model. The experimental data of the fusion cross
sections for Ca+Zr at the energy near barrier can be
reproduced remarkably well without introducing any new parameters. The
mechanism for the enhancement of fusion probability for fusion reactions with
neutron-rich projectile or target is analyzed.Comment: 20 pages, 12 figures, 3 table
Peripheral N Scattering: A Tool For Identifying The Two Pion Exchange Component Of The NN Potential
We study elastic N scattering and produce a quantitative correlation
between the range of the effective potential and the energy of the system. This
allows the identification of the waves and energies for which the scattering
may be said to be peripheral. We then show that the corresponding phase shifts
are sensitive to the tail of the NN potential, which is due to the exchange of
two pions. However, the present uncertainties in the experimental phase shifts
prevent the use of N scattering to discriminate the existing models
for the NN interaction.Comment: 19 pages, 6 PostScript figures, RevTeX, to be appear in Phys. Rev.
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