4,447 research outputs found
A consistent four-body CDCC model of low-energy reactions: Application to 9Be + 208Pb
We investigate the Be + Pb elastic scattering, breakup and fusion
at energies around the Coulomb barrier. The three processes are described
simultaneously, with identical conditions of calculations. The Be nucleus
is defined in an + n three-body model, using the
hyperspherical coordinate method. We first analyze spectroscopic properties of
Be, and show that the model provides a fairly good description of the
low-lying states. The scattering with Pb is then studied with the
Continuum Discretized Coupled Channel (CDCC) method, where the
+ n continuum is approximated by a discrete number of pseudostates. Optical
potentials for the + Pb and n+ Pb systems are taken
from the literature. We present elastic-scattering and fusion cross sections at
different energies.Comment: 8 pages, 3 figures, Proceedings of the International Conference on
Nucleus-Nucleus Collisions, NN 2015, Catania-Italy. arXiv admin note:
substantial text overlap with arXiv:1410.641
Estudio palinológico en las especies ibéricas del género Serratula L. (Asteraceae)
Se estudian 28 poblac i ones pol ínicas pertenecientes a l os 14 táxones del género Scrratula L. (sect . Serra tula y sect . Klasea} de l a Península Ibéri ca , tanto al microscopio óptico como a l microscopio e l ectrónico de barrido . Se describen cuatro tipos polinices y se pone de manifi esto que las principal es diferencias a ni ve l de sección se r efieren a l a estructura y ornamentación de la exinaSorne 28 lber ian populati ons of 14 taxa o f the genus Serratula L . (sect . Serratula and sect . Klasea) have been stud i ed , both 111ith light microscopy and scann i ng el ectron mic roscopy. Four pol len t ypes are described and the impor t ance of exi ne characters for separ a t i ng each of t he two sections i s di scusse
Modeling Nonaxisymmetric Bow Shocks: Solution Method and Exact Analytic Solutions
A new solution method is presented for steady-state, momentum-conserving,
non-axisymmetric bow shocks and colliding winds in the thin-shell limit. This
is a generalization of previous formulations to include a density gradient in
the pre-shock ambient medium, as well as anisotropy in the pre-shock wind. For
cases where the wind is unaccelerated, the formalism yields exact, analytic
solutions.
Solutions are presented for two bow shock cases: (1) that due to a star
moving supersonically with respect to an ambient medium with a density gradient
perpendicular to the stellar velocity, and (2) that due to a star with a
misaligned, axisymmetric wind moving in a uniform medium. It is also shown
under quite general circumstances that the total rate of energy thermalization
in the bow shock is independent of the details of the wind asymmetry, including
the orientation of the non-axisymmetric driving wind, provided the wind is
non-accelerating and point-symmetric. A typical feature of the solutions is
that the region near the standoff point is tilted, so that the star does not
lie along the bisector of a parabolic fit to the standoff region. The principal
use of this work is to infer the origin of bow shock asymmetries, whether due
to the wind or ambient medium, or both.Comment: 26 pages and 6 figures accepted to ap
Assessing the adequacy of the bare optical potential in near-barrier fusion calculation
We critically examine the differences among the different bare nuclear
interactions used in near-barrier heavy ion fusion analysis and
Coupled-Channels calculations, and discuss the possibility of extracting the
barrier parameters of the bare potential from above-barrier data. We show that
the choice of the bare potential may be critical for the analysis of the fusion
cross sections. We show also that the barrier parameters taken from above
barrier data may be very wrong.Comment: 8 pages, 3 tables, 8 figures. Submitted to Physical Review
Continuum-continuum coupling and polarization potentials for weakly bound system
We investigate the influence of couplings among continuum states in
collisions of weakly bound nuclei. For this purpose, we compare cross sections
for complete fusion, breakup and elastic scattering evaluated by continuum
discretized coupled channel (CDCC) calculations, including and not including
these couplings. In our study, we discuss this influence in terms of the
polarization potentials that reproduce the elastic wave function of the coupled
coupled channel method in single channel calculations. We find that the
inclusion of couplings among the continuum states renders the real part of the
polarization potential more repulsive, whereas it leads to weaker apsorption to
the breakup channel. We show that the non-inclusion of continuum-continuum
couplings in CDCC calculations may not lead to qualitative and quantitative
wrong conclusions.Comment: 4 pages, 4 figures. Submitted to Phys. Rev.
Complete Fusion Enhancement and Suppression of Weakly Bound Nuclei at Near Barrier Energies
We consider the influence of breakup channels on the complete fusion of
weakly bound systems in terms of dynamic polarization potentials. It is argued
that the enhancement of the cross section at sub-barrier energies may be
consistent with recent experimental observations that nucleon transfer, often
leading to breakup, is dominant compared to direct breakup. The main trends of
the experimental complete fusion cross section for Li + Bi are
analyzed in the framework of the DPP approach.Comment: 12 pages, 2 figure
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