103 research outputs found
Exit Doorway Model for Nuclear Breakup of Weakly Bound Projectiles
We derive closed expressions for the nuclear breakup cross sections in the
adiabatic limit using the Austern-Blair theory. These expressions are
appropriate for the breakup of weakly bound nuclei. The concept of an exit
doorway that mediates the coupling between the entrance channel and the breakup
continuum is used. We prove the validity of the scaling law that dictates that
the nuclear breakup cross section scales linearly with the radius of the
target. We also compare our results for the nuclear breakup cross section of
Be, B on several targets with recent CDCC calculation.Comment: 5 pages, 1 figur
Higher order effects in the and transfer reactions
Full Coupled Channels Calculations were performed for the
and transfer reactions at several deuteron incident
energies from MeV up to 3.27 MeV. A strong polarization effect
between the entrance channel and the transfer channels
and was
observed. This polarization effect had to be taken into account in order to
obtain realistic spectroscopic factors from these reactions.Comment: 15 papes, 13 figures, accepted for publication in Phys. Rev.
A schematic model for the direct cross-section in reactions induced by exotic and stable projectiles
A geometric model for the direct contribution of the reaction cross section
induced by light ions on different targets is presented. The model separates
the total reaction cross section into two components, one for total fusion and
another for direct reactions. We show that the direct part scales as , where is related to the nuclear radius and is the width of a ring,
which is related to the nuclear diffuseness. A simple expression is presented
to calculate the radius and the width parameter in terms of the masses
and charges of the system. The method is applied to experimental data of
exotic, weakly bound, and strongly bound projectiles on several targets.
Different diffuseness parameters were obtained for different types of
projectiles: exotic n-rich, stable weakly bound, stable strongly bound and
exotic p-rich exotic projectiles.Comment: 10 pages, 4 figures, 2 table
Comparison of 120Sn(6He,6He)120Sn and 120Sn(alpha,alpha)120Sn elastic scattering and signatures of the 6He neutron halo in the optical potential
Cross sections of Sn(,)Sn elastic scattering
have been extracted from the particle beam contamination of a recent
Sn(He,He)Sn experiment. Both reactions are analyzed
using systematic double folding potentials in the real part and smoothly
varying Woods-Saxon potentials in the imaginary part. The potential extracted
from the Sn(He,He)Sn data may be used as the basis for
the construction of a simple global He optical potential. The comparison of
the He and data shows that the halo nature of the He nucleus
leads to a clear signature in the reflexion coefficients : the relevant
angular momenta with and are shifted to
larger with a broader distribution. This signature is not present in the
scattering data and can thus be used as a new criterion for the
definition of a halo nucleus.Comment: 13 pages, 7 figures, accepted for publication in Phys. Rev.
Elastic Scattering and Total Reaction Cross Section for the 6He + 27Al System
The elastic scattering of the radioactive halo nucleus 6He on 27Al target was
measured at four energies close to the Coulomb barrier using the RIBRAS
(Radioactive Ion Beams in Brazil) facility. The Sao Paulo Potential(SPP) was
used and its diffuseness and imaginary strength were adjusted to fit the
elastic scattering angular distributions. Reaction cross-sections were
extracted from the optical model fits. The reduced reaction cross-sections of
6He on 27Al are similar to those for stable, weakly bound projectiles as
{6,7}Li, 9Be and larger than stable, tightly bound projectile as 16O on 27Al.Comment: 7 pages, 1 table, 3 figure
Elastic scattering and total reaction cross sections for the 8Li + 12C system
The elastic-scattering angular distribution for 8Li on 12C has been measured at ELAB=23.9 MeV with 8Li radioactive nuclear beam produced by the Radioactive Ion Beams in Brazil facility. This angular distribution was analyzed in terms of optical-model with Woods-Saxon and double-folding São Paulo potential. The roles of the breakup and inelastic channels were also investigated with cluster folding and deformed potentials, respectively, through coupled-channels calculations. The angular distribution for the proton-transfer 12C(8Li,9Be)11B reaction was also measured at the same energy. The spectroscopic factor for the 9Be|8Li+p bound system was obtained and compared with shell-model calculations and with other experimental values. Total reaction cross sections for the present system were also extracted from the elastic-scattering analysis. A systematic of the reduced reaction cross sections obtained from the present and published data on 6,7,8Li isotopes on 12C was performed as a function of energy
Measurements of the 25 Mg( 11 B , 12 C) 24 Na and 25 Mg( 11 B , 10 Be) 26 Al proton transfer reactions
Angular distributions for the 11 B+25 Mg elastic scattering, 25 Mg (11B, 12 C) 24 Na proton pickup, and 25 Mg (11 B, 10 Be) 26 Al stripping reactions have been measured at E11 B=35 MeV. The angular distributions have been analyzed by the distorted-waves Born approximation calculations using the code fresco. The spectroscopicfactors for the overlaps 25 Mg | 26 Al , 25 Mg | 24 Na for the ground state and excited states of 26 Al and 24 Na have been obtained and compared to previous measurements and shell-model calculations.FAPESP 01/06676-
Spectroscopy of high-lying resonances in 9 Be by the measurement of ( p , p ), ( p , d ), and ( p , α ) reactions with a radioactive 8 Li beam
We measured the
8
Li
(
p
,
p
)
8
Li
,
8
Li
(
p
,
d
)
7
Li
, and
8
Li
(
p
,
α
)
5
He
reactions at low energies using the thick target inverse kinematics method, with a polyethylene
[
CH
2
]
n
target and a radioactive
8
Li
beam available at the Radioactive Ion Beams in Brazil facility of São Paulo. By measuring simultaneously several reaction channels
(
p
,
p
)
,
(
p
,
d
)
, and
(
p
,
α
)
, the still uncertain high-lying resonances of
9
Be
, close to the proton threshold, can be studied and their parameters, such as energy, width, and spin parity can be more reliably determined. The experimental excitation functions of the reactions
8
Li
(
p
,
p
)
8
Li
,
8
Li
(
p
,
d
)
7
Li
, and
8
Li
(
p
,
α
)
5
He
were analyzed using the
R
-matrix theory, which allows us to infer the properties of the resonances. Multichannel
R
-matrix analysis provides evidence for a significant clustering in the
(
p
,
d
)
channel. The experimental data and the multichannel
R
-matrix analysis will be presented.Fundação de Amparo à Pesquisa do Estado de São Paulo. Brasil. (FAPESP) 2011/15904-7, 2013/22100-7 y 2016/21434-7VI Plan Propio de Investigación de la Universidad de Sevilla. España. (2017–2018
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