51 research outputs found
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.
Two-neutron transfer in 7 Be + 9 Be collisions
Elastic scattering and transfer cross sections for the
7
Be
+
9
Be
system have been measured at
E
lab
=
23.1
MeV
using the
7
Be
radioactive secondary beam produced at Radioactive Ion Beams in Brazil facility at the University of São Paulo. The elastic scattering has been measured by detecting the
7
Be
scattered at forward angles in the laboratory system. The transfer reaction
9
Be
(
7
Be
,
9
Be
)
7
Be
was identified by detecting the
9
Be
scattered at the same laboratory angles. The elastic angular distribution has been analyzed by optical model calculations using a Woods-Saxon form factor whose parameters have been varied to best reproduce the experimental data at forward angles. Coupled reaction channels calculations (CRC) have been performed to describe the transfer, considering the coupling to the transfer channel and including contributions to the ground state and to the first excited state of
7
Be
(
1
/
2
−
;
429
keV
) in the final state. The spectroscopic amplitudes used in the CRC calculation have been derived from shell-model calculations. Similar CRC calculations were applied to existing
9
Be
(
p
,
t
)
7
Be
data to check the consistency of our results results for the (
7
Be
,
9
Be
) transfer reaction.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) de Brasil, Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) de Brasil y Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) de Brasil. 2013/22100-7 y 2016/21434-
Two-neutron transfer in the 6 He + 120 Sn reaction
A large yield of
α
particles produced in the
120
Sn
(
6
He
,
α
)
reaction was measured at 20.3-, 22.2-, 22.4-, and 24.5-MeV bombarding energies. The
α
particles are distributed over a broad energy range in the vicinity and below the elastic scattering
6
He
peak. Energy integrated
α
-particle cross sections have been obtained at
θ
lab
=
36
∘
,
40
∘
, and
60
∘
. The
α
energy distributions have been analyzed at a fixed laboratory angle
(
≈
60
∘
)
in terms of the reaction
Q
value, considering the
2
n
-transfer reaction kinematics
120
Sn
(
6
He
,
α
)
122
Sn
. A kinematical analysis of the
Q
-value distribution shows that the recoil system
120
Sn
+
2
n
is formed in highly excited states in the continuum, at increasing excitation energies as the bombarding energy increases. It is shown that by using Brink's formula, the excitation energy depends on the transferred angular momentum following a linear relation with the square of the angular momentum, indicating that some kind of dinuclear rotating system is formed after the reaction.Conselho Nacional de Desenvolvimento Científico e Tecnológico-CNPq/MCTI de Brasil y Fundação de Amparo à Pesquisa do Estado de São Paulo. Brasil–FAPESP. 2013/22100-7 y 2014/19666-1VI Plan Propio de Investigación de la Universidad de Sevilla (2017-2018
Experimental study of He6+Be9 elastic scattering at low energies
New data for the He6+Be9 reaction at Elab=16.2 and 21.3 MeV have been taken and analyzed. The effect of the collective couplings to the excited states of the target has been studied by means of coupled-channels calculations, using a double-folding potential for the bare interaction between the colliding nuclei, supplemented with a phenomenological imaginary part of Woods-Saxon type. In addition, three- and four-body continuum-discretized coupled-channels calculations have been performed to investigate the effect of the projectile breakup on the elastic scattering. Both effects, the coupling to target and projectile excited states, are found to affect significantly the elastic scattering. The trivial local polarization potential extracted from the continuum-discretized coupled-channels calculations indicates that continuum couplings produce a repulsive real part and a long-range imaginary part in the projectile-target interaction. © 2011 American Physical Society.This work has been partially supported by the Spanish Ministerio de Ciencia e Innovacion´ under Projects FPA2009-07653 and PCI2006-A7-0654 and by the Spanish Consolider-Ingenio 2010 Programme CPAN (CSD2007-00042).Peer Reviewe
Study of the 6He+9Be and 7Be+9Be collisions
We present elastic scattering angular distributions of the 6He+9Be and 7Be+9Be reactions at Elab =16.2 MeV and Elab =23.7 MeV respectively. The 6He+9Be measurements have been performed at the Pelletron Laboratory of the Institute of Physics of the University of Sao Paulo, Brazil, using the Radioactive Ion Beams in Brasil (RIBRAS) facility and the 7Be+9Be system has beenmeasured at CRC Radioactive Beam Facility at Louvain-la-Neuve,Belgium. An OpticalModel analysis has been performed to obtain the nuclear potentials for both systems. A coupled-channel calculation was performed for the 7Be+9Be system taking into account the coupling to the first excited state and breakup channels of the 7Be nucleus. Keywords: Radioctive Beams. Exotic Nuclei. Nuclear Halo. Long range absorption. Elastic Scattering. Optical potential. Coupled channels calculations. PACS: 25.60.-t,25.60.Bx,25.70.Bc,29.38.-c,24.10.E
Ionization and Fragmentation of a Global Warming Gas by EUV and X-Ray Photons
An experimental investigation of the processes leading tothe fragmentation of the singly ionized 1,1,1,2-tetrafluoroethane (HFC-134a, CH2FCF3) by EUV and soft X-rays is presented. HFC-134ais taken into consideration as the most convenient replacement for CFC-12 in refrigeration applications due to the fact that it has null ozone depletion factor. Dissociation of the singly ionized HFC-134amolecule was induced by valence, direct and indirect C 1s core photoionization or photoexcitation and the ionic fragments were detected in coincidence (PEPICO mode) with the ejected electrons without energy analysis. The singly ionized parent ion CF4CH2+can be detected even at photon energies above the C 1s threshold
Study of reactions induced by 6He on 9Be
We present the results of experiments using a 6He beam on a 9Be target at\ud
energies 7 − 9 times the Coulomb barrier. Angular distributions of the elastic, inelastic\ud
scattering (target breakup) and the -particle production in the 6He+9Be collision have\ud
been analysed. Total reaction cross sections were obtained from the elastic scattering\ud
analyses and a considerable enhancement has been observed by comparing to stable systems.FAPESPFundação Araucári
Purification and In Situ Immobilization of Papain with Aqueous Two-Phase System
Papain was purified from spray-dried Carica papaya latex using aqueous two-phase system (ATPS). Then it was recovered from PEG phase by in situ immobilization or preparing cross-linked enzyme aggregates (CLEAs). The Plackett-Burman design and the central composite design (CCD) together with the response surface methodology (RSM) were used to optimize the APTS processes. The highly purified papain (96–100%) was achieved under the optimized conditions: 40% (w/w) 15 mg/ml enzyme solution, 14.33–17.65% (w/w) PEG 6000, 14.27–14.42% (w/w) NaH2PO4/K2HPO4 and pH 5.77–6.30 at 20°C. An in situ enzyme immobilization approach, carried out by directly dispersing aminated supports and chitosan beads into the PEG phase, was investigated to recover papain, in which a high immobilization yield (>90%) and activity recovery (>40%) was obtained. Moreover, CLEAs were successfully used in recovering papain from PEG phase with a hydrolytic activity hundreds times higher than the carrier-bound immobilized papain
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