1,929 research outputs found
Nuclear Breakup of Borromean Nuclei
We study the eikonal model for the nuclear-induced breakup of Borromean
nuclei, using Li11 and He6 as examples. The full eikonal model is difficult to
realize because of six-dimensional integrals, but a number of simplifying
approximations are found to be accurate. The integrated diffractive and
one-nucleon stripping cross sections are rather insensitive to the
neutron-neutron correlation, but the two-nucleon stripping does show some
dependence on the correlation. The distribution of excitation energy in the
neutron-core final state in one-neutron stripping reactions is quite sensitive
to the shell structure of the halo wave function. Experimental data favor
models with comparable amounts of s- and p-wave in the Li11 halo.Comment: 34 pages REVTeX, 14 postscript figures. Small changes in comparison
with experimen
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.
Density dependence of in-medium nucleon-nucleon cross sections
The lowest-order correction of the density dependence of in-medium
nucleon-nucleon cross sections is obtained from geometrical considerations of
Pauli-blocking effects. As a by-product, it is shown that the medium
corrections imply an 1/E energy dependence of the density-dependent term.Comment: 7 pages, 1 figur
Systematics of quadrupolar correlation energies
We calculate correlation energies associated with the quadrupolar shape
degrees of freedom with a view to improving the self-consistent mean-field
theory of nuclear binding energies. The Generator Coordinate Method is employed
using mean-field wave functions and the Skyrme SLy4 interaction. Systematic
results are presented for 605 even-even nuclei of known binding energies, going
from mass A=16 up to the heaviest known. The correlation energies range from
0.5 to 6.0 MeV in magnitude and are rather smooth except for large variations
at magic numbers and in light nuclei. Inclusion of these correlation energies
in the calculated binding energy is found to improve two deficiencies of the
Skyrme mean field theory. The pure mean field theory has an exaggerated shell
effect at neutron magic numbers and addition of the correlation energies reduce
it. The correlations also explain the phenomenon of mutually enhanced magicity,
an interaction between neutron and proton shell effects that is not explicable
in mean field theory.Comment: 4 pages with 3 embedded figure
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
Time-dependent density functional theory for strong electromagnetic fields in crystalline solids
We apply the coupled dynamics of time-dependent density functional theory and
Maxwell equations to the interaction of intense laser pulses with crystalline
silicon. As a function of electromagnetic field intensity, we see several
regions in the response. At the lowest intensities, the pulse is reflected and
transmitted in accord with the dielectric response, and the characteristics of
the energy deposition is consistent with two-photon absorption. The absorption
process begins to deviate from that at laser intensities ~ 10^13 W/cm^2, where
the energy deposited is of the order of 1 eV per atom. Changes in the
reflectivity are seen as a function of intensity. When it passes a threshold of
about 3 \times 1012 W/cm2, there is a small decrease. At higher intensities,
above 2 \times 10^13 W/cm^2, the reflectivity increases strongly. This behavior
can be understood qualitatively in a model treating the excited electron-hole
pairs as a plasma.Comment: 27 pages; 11 figure
Extracting particle freeze-out phase-space densities and entropies from sources imaged in heavy-ion reactions
The space-averaged phase-space density and entropy per particle are both
fundamental observables which can be extracted from the two-particle
correlation functions measured in heavy-ion collisions. Two techniques have
been proposed to extract the densities from correlation data: either by using
the radius parameters from Gaussian fits to meson correlations or by using
source imaging, which may be applied to any like pair correlation. We show that
the imaging and Gaussian fits give the same result in the case of meson
interferometry. We discuss the concept of an equivalent instantaneous source on
which both techniques rely. We also discuss the phase-space occupancy and
entropy per particle. Finally, we propose an improved formula for the
phase-space occupancy that has a more controlled dependence on the uncertainty
of the experimentally measured source functions.Comment: 14 pages, final version, to appear PRC. Fixed typos, added refs. for
last section, added discussions of imaging and d/p ratio
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