1,542 research outputs found
The Spectral Line Shape of Exotic Nuclei
The quadrupole strength function of is calculated making use of the
SIII interaction, within the framework of continuum-RPA and taking into account
collisions among the nucleons (doorway coupling). The centroid of the giant
resonance is predicted at MeV, that is much below the energy
expected for both isoscalar and isovector quadrupole resonances in nuclei along
the stability valley. About half of this width arises from the coupling of the
resonance to the continuum and about half is due to doorway coupling. This
result is similar to that obtained in the study of giant resonances in light,
-stable nuclei, and shows the lack of basis for the expectation,
entertained until now in the literature, that continuum decay was the main
damping mechanism of giant resonances in halo nuclei.Comment: LaTeX file, 7 pages, figures not included but available if requested
at [email protected], accepted for publication in Phys. Rev.
How harmonic is dipole resonance of metal clusters?
We discuss the degree of anharmonicity of dipole plasmon resonances in metal
clusters. We employ the time-dependent variational principle and show that the
relative shift of the second phonon scales as in energy, being
the number of particles. This scaling property coincides with that for nuclear
giant resonances. Contrary to the previous study based on the boson-expansion
method, the deviation from the harmonic limit is found to be almost negligible
for Na clusters, the result being consistent with the recent experimental
observation.Comment: RevTex, 8 page
Observations of medium energy gamma ray emission from the galactic center region
Measurements of the gamma-ray emission in the medium energy range between 15 and 100 MeV, obtained during two ballon flights from Brazil are presented. The importance of this energy region in determining whether pi deg - decay of electron bremsstrahlung is the most likely dominant source mechanism is discussed along with the implications of such observations. Specifically, the data from this experiment suggest that emission from the galactic plane is similar to theoretical spectrum calculations including both sources mechanisms, but with the bremsstrahlung component enhanced by a factor of about 2. A spectral distribution of gamma-rays produced in the residual atmosphere above the instrument is also presented and compared with other data. A rather smooth spectral variation from high to low energies is found for the atmospheric spectrum
Collective oscillations of a trapped Fermi gas near the unitary limit
We calculate the oscillation frequencies of trapped Fermi condensate with
particular emphasis on the equation of state of the interacting Fermi system.
We confirm Stringari's finding that the frequencies are independent of the
interaction in the unitary limit, and we extend the theory away from that
limit, where the interaction does affect the frequencies of the compressional
modes only.Comment: 4 pages, corrected a couple of trivial mistakes in table II and the
related text and added reference
Feshbach Resonances and Limiting Thermodynamics of Strongly Correlated Nucleons
A finite temperature model of strongly correlated nucleons with underlying
isospin symmetries is developed. The model can be used to study the role of
bound states and Feshbach resonances on the thermal properties of a spin 1/2,
isospin 1/2 system of protons and neutrons by varying the proton fraction. An
analysis of features associated with a universal thermodynamic limit or unitary
limit is given. In the limit of very large scattering length, the effective
range to quantum thermal wavelength appears as a limiting scale in an
interaction energy and equation of state.Comment: 8 pages, 4 figure
Exact solutions for interacting boson systems under rotation
We study a class of interacting, harmonically trapped boson systems at
angular momentum L. The Hamiltonian leaves a L-dimensional subspace invariant,
and this permits an explicit solution of several eigenstates and energies for a
wide class of two-body interactionsComment: 8 pages, error corrected (concerns generalization of subspace
structure
Comparison of Transfer-to-Continuum and Eikonal Models of Projectile Fragmentation Reactions
Spectroscopic properties of nuclei are accessible with projectile
fragmentation reactions, but approximations made in the reaction theory can
limit the accuracy of the determinations. We examine here two models that have
rather different approximations for the nucleon wave function, the target
interaction, and the treatment of the finite duration of the reaction. The
nucleon-target interaction is treated differently in the eikonal and the
transfer-to-continuum model, but the differences are more significant for light
targets. We propose a new parameterization with that in mind. We also propose a
new formula to calculate the amplitude that combines the better treatment of
the wave function in the eikonal model with the better treatment of the target
interaction in the transfer-to-continuum model.Comment: 21 pages, latex file including 3 tables. 5 figures. Submitted to
Phys. Rev.
Three-body Faddeev Calculation for 11Li with Separable Potentials
The halo nucleus Li is treated as a three-body system consisting of an
inert core of Li plus two valence neutrons. The Faddeev equations are
solved using separable potentials to describe the two-body interactions,
corresponding in the n-Li subsystem to a p resonance plus a
virtual s-wave state. The experimental Li energy is taken as input and
the Li transverse momentum distribution in Li is studied.Comment: 6 pages, RevTeX, 1 figur
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