379 research outputs found
The Effect of Nuclear Rotation on the Collective Transport Coefficients
We have examined the influence of rotation on the potential energy and the
transport coefficients of the collective motion (friction and mass
coefficients). For axially symmetric deformation of nucleus Th-224 we have
found that at excitations corresponding to temperatures T > 1 MeV the shell
correction to the liquid drop energy practically does not depend on the angular
rotation. The friction and mass coefficients obtained within the linear
response theory for the same nucleus at temperatures larger than T=2 MeV are
rather stable with respect to rotation provided that the contributions from
spurious states arising due to the violation of rotation symmetry are removed.
At smaller excitations both friction and mass parameters corresponding to the
elongation mode are growing functions of rotational frequency.Comment: 16 pages, 5 eps figures, Latex, submitted to Nucl.Phys.
Diamond thin Film Detectors for Beam Monitoring Devices
Diamonds offer radiation hard sensors, which can be used directly in primary
beams. Here we report on the use of a polycrystalline CVD diamond strip sensor
as beam monitor of heavy ion beams with up to 2.10^9 lead ions per bunch. The
strips allow for a determination of the transverse beam profile to a fraction
of the pitch of the strips, while the timing information yields the
longitudinal bunch length with a resolution of the order of a few mm.Comment: 6 pages, 7 figures, to appear in the Proceedings of the Hasselt
Diamond Workshop (Hasselt, Belgium, Feb. 2006), v4: accidentally submitted
figure, appearing at end, remove
Nuclear and Neutron Star Radii
We investigate the correlation between nuclear neutron radii and the radius
of neutron stars. We use a well-established hadronic SU(3) model based on
chiral symmetry that naturally includes non-linear vector meson and scalar
meson - vector meson couplings. The relative strengths of the couplings modify
the nuclear isospin-dependent interactions. We study the dependence of nuclear
and neutron star radii on the coupling strengths. The relevance of the results
for parity-violating electron-nucleus scattering and the URCA process in
neutron stars is discussed
Collective Quadrupole Excitations in Transitional Nuclei
The generalized Bohr Hamiltonian was used to describe the low-lying collective excitations in even-even isotopes of Ru, Pd, Te, Ba and Nd. The Strutinsky collective potential and cranking inertial functions were obtained using the Nilsson potential. The effect of coupling with the pairing vibrations is taken into account approximately when determining the inertial functions. The calculation does not contain any free parameter
Contact-induced spin polarization in carbon nanotubes
Motivated by the possibility of combining spintronics with molecular
structures, we investigate the conditions for the appearance of
spin-polarization in low-dimensional tubular systems by contacting them to a
magnetic substrate. We derive a set of general expressions describing the
charge transfer between the tube and the substrate and the relative energy
costs. The mean-field solution of the general expressions provides an
insightful formula for the induced spin-polarization. Using a tight-binding
model for the electronic structure we are able to estimate the magnitude and
the stability of the induced moment. This indicates that a significant magnetic
moment in carbon nanotubes can be observed.Comment: To appear in Phys. Rev. B (2003
The Neutron Halo in Heavy Nuclei Calculated with the Gogny Force
The proton and neutron density distributions, one- and two-neutron separation
energies and radii of nuclei for which neutron halos are experimentally
observed, are calculated using the self-consistent Hartree-Fock-Bogoliubov
method with the effective interaction of Gogny. Halo factors are evaluated
assuming hydrogen-like antiproton wave functions. The factors agree well with
experimental data. They are close to those obtained with Skyrme forces and with
the relativistic mean field approach.Comment: 13 pages in Latex and 17 figures in ep
Evidence for the Jacobi shape transition in hot 46Ti
The gamma-rays from the decay of the GDR in 46Ti compound nucleus formed in
the 18O+28Si reaction at bombarding energy 105 MeV have been measured in an
experiment using a setup consisting of the combined EUROBALL IV, HECTOR and
EUCLIDES arrays. A comparison of the extracted GDR lineshape data with the
predictions of the thermal shape fluctuation model shows evidence for the
Jacobi shape transition in hot 46Ti. In addition to the previously found broad
structure in the GDR lineshape region at 18-27 MeV caused by large
deformations, the presence of a low energy component (around 10 MeV), due to
the Coriolis splitting in prolate well deformed shape, has been identified for
the first time.Comment: 8 pages, 4 figures, proceedings of the COMEX1 conference, June 2003,
Paris; to be published in Nucl. Phys.
Radiative electron capture in the first forbidden unique decay of 81Kr
The photon spectrum accompanying the orbital K-electron capture in the first
forbidden unique decay of 81Kr was measured. The total radiation intensity for
the photon energies larger than 50 keV was found to be 1.47(6) x 10^{-4} per
K-capture. Both the shape of the spectrum and its intensity relative to the
ordinary, non-radiative capture rate, are compared to theoretical predictions.
The best agreement is found for the recently developed model which employs the
length gauge for the electromagnetic field.Comment: 7 pages, 6 figure
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