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

Almeida, Viviane Morcelle de

Assuncao, Marlete Pereira Meira de

Barioni, Adriana

Condori, Ruben Pampa

Faria, Pedro Neto de

Fonseca, Leandro Milhomens da

Guimaraes, Valdir

Leistenschneider, Erich

Lepine, Alinka

Lichtenthaler Filho, Rubens

Mendes Junior, Djalma Rosa

Morais, Maria Carmen

Moro, A. M.

Nassar, T. B.

Pires, Kelly Cristina Cezaretto

Rodriguez-Gallardo, M.

Scarduelli, Valdir Brunetti

Shorto, Julian Marco Barbosa

Zagatto, Vinicius Antonio Bocaline

Zamora, J. C.

Biblioteca Digital da Produção Intelectual da Universidade de São Paulo (BDPI/USP)

Study of reactions induced by 6He on 9Be
K.C.C. Pires1,a, R. Lichtenthäler2, A. M. Moro3, M. Rodriguez-Gallardo3, A. Lépine-Szily2, V.
Guimarães2, P. N. Faria4, A. Barioni5, D.R. Mendes Junior4, M. Assunção6, M.C. Morais2, V.
Morcelle4,b, J.M.B. Shorto7, R. Pampa-Condori2, V. Scarduelli2, E. Leistenschneider2, L. M.
Fonseca2, V. Zagatto2, T. B. Nassar6, and J. C. Zamora8
1Universidade Tecnológica Federal do Paraná, Cornélio Procópio, Brazil
2Departamento de Física Nuclear, Instituto de Física, Universidade de São Paulo, Brazil
3Departmento de Física Atomica, Molecular y Nuclear, Universidad de Sevilla, Spain
4Instituto de Física, Universidade Federal Fluminense, Rio de Janeiro, Brazil
5Instituto de Física, Universidade Federal da Bahia, Brazil
6Departamento de Ciências Exatas e da Terra, Universidade Federal de São Paulo, Brazil
7Instituto de Pesquisa Energeticas e Nucleares, Comissão Nacional de Energia Nuclear, São Paulo, Brazil
8Technische Universität Darmstadt, Germany
Abstract. We present the results of experiments using a 6He beam on a 9Be target at
energies 7 − 9 times the Coulomb barrier. Angular distributions of the elastic, inelastic
scattering (target breakup) and the α-particle production in the 6He+9Be collision have
been analysed. Total reaction cross sections were obtained from the elastic scattering
analyses and a considerable enhancement has been observed by comparing to stable sys-
tems.
1 Introduction and Experimental Setup
Current experiments with reactions induced by exotic and weakly bound projectiles on heavy targets
show interesting phenomena, such as the anomalously large values of the reaction cross sections [1–
5], and long range absorption effects [1, 6]. This work has been performed to investigate if the same
holds for collisions with lighter targets, for which the Coulomb breakup is expected to be small.
The 6He+9Be measurements were performed using the RIBRAS facility [7] installed at the 8-
UD Pelletron Tandem accelerator Laboratory of the University of Sao Paulo. The RIBRAS system
consists of two superconducting solenoids of 6.5 T maximum central field. The 6He secondary beam,
with intensity about 2.4 × 104 pps, was produced by the 9Be(7Li,6He) reaction with a 7Li primary
beam of 300 nAe. The detection system consisted of four ∆E-E silicon telescopes, with 20 microns
and 1000 microns of thickness, respectively, which allowed the identification of the 6He particles from
the 7Li beam contaminant and light particles.
We have measured angular distributions for elastic scattering and α-particle production from the
interaction of 6He on secondary targets of 9Be (1.93 mg/cm2) and 197Au (2.95 mg/cm2) at the energies
ae-mail: kellypires@utfpr.edu.br
bPresent address: Universidade Federal de Itajubá, Campus Itabira, Minas Gerais, Brazil
DOI: 10.1051/
C© Owned by the authors, published by EDP Sciences, 2014
,
/
03071 (2014)
201
66
epjconf
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This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits 
unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 
Article available at http://www.epj-conferences.org or http://dx.doi.org/10.1051/epjconf/20146603071
Elab=16.2 MeV and Elab=21.3 MeV, between 15◦ and 75◦ in steps of 3◦ in the laboratory system. The
gold target was used for normalization and monitoring since the collision 6He+197Au at these energies
are pure Rutherford. The Coulomb barrier for 6He+9Be system is EB=2.22 MeV and for 6He+197Au
system is EB=22.40 MeV. Typical biparametric ∆E-E spectra obtained in these experiments are shown
in Figure 1.
Figure 1. Biparametric spectra obained with 6He beam on (a) 9Be, (b) 197Au targets at θlab=15◦ at Elab=16.2 MeV.
The 7Li and 4He elastic scattering peaks, at ETOT AL around 1100 and 2350 channels respectively, come from the
primary beam (contamination) and are indicated by arrows.
2 Data Analysis and Results
The 6He+9Be elastic scattering angular distributions have been obtained and were analysed by Cou-
pled Channels (CC) calculations considering the 9Be target excitation as well as by 3-body and 4-body
Continuum-Discretization Coupled-Channels (CDCC) calculations including explicitly the breakup of
the 6He nucleus. The results of these calculations are shown in Figure 2 and more details are given in
Ref. [6].
0 30 60 9010
-2
10-1
100
101
σ
/σ
R
ut
h
 θ
 c.m.
 (deg)
(a) (b)
Ref. [6]Ref. [6]OM (bare)
CC
3b-CDCC
4b-CDCC
RIBRAS data 
0 30 60 90 120
θ
c.m. 
(deg)
E=21.3 MeVE=16.2 MeV
Figure 2. 6He+9Be elastic scattering angular distributions compared with several theoretical calculations at (a)
Elab=16.2 MeV and (b) Elab=21.3 MeV.
It is important to mention that the 3-body CDCC calculations presented in Figure 2 describe the
6He states using an effective two body Hamiltonian (2n+4He) which reproduces the 6He rms [8].
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Nevertheless the 4-body calculations still present a reduced cross-section compared to the 3-body
case, mainly at backward angles, which is not seen in the experimental data.
In addition to the interacting potentials, the elastic scattering calculations provide information
of the total reaction cross section. For the analyses presented here (CC, 3b-CDCC, 4b-CDCC), the
average total reaction cross sections are 1525(104) mb and 1527(106) mb, respectively for 16.2 MeV
and 21.3 MeV energies. These are relatively large values even when compared to the reaction cross
sections for weakly bound stable projectiles, indicating that there is an enhancement of about 25 % in
the total reaction cross section for the 6He+9Be system with respect to stable systems.
Besides the elastic scattering events, a large α-particle production is observed in the biparametric
∆E-E spectrum (see Figure 1) obtained with 9Be target, which is not present in the spectrum with
gold target [4]. It is to be noted that for 6He+197Au system, the energy is below the Coulomb barrier
whereas for 6He+9Be case the energy is about 7−9 times the Coulomb barrier. It means that only a few
reaction channels are open for the 6He+197Au case and Figure 1-(b) basically shows the beam content.
The intensities of the contaminant beams have been obtained from a measurement performed at zero
degrees using a fainted beam and are approximately 68.2% for the 7Li, 7.7% for 4He, 15.7% for 6He
and 8.4% for lighter particles p, d, t. Indeed, the large yield of α-particles produced in the 6He+9Be
collision indicates a large reaction cross section. We performed an estimation of the diferential α-
particle production cross section by integrating in energy the α-counts and considering the total beam
intensity, including the contaminants, and the cross sections range from 15 to 330 mb/sr in the angular
range of the measurements.
Moreover, events related to the 6He nucleus with energy smaller than the elastic scattering peak
were observed in Figure 1-(a). These events are related to processes where the identity of the 6He
beam particles is preserved but not their energies and could correspond to the excitation of the 9Be
target since the 6He nucleus has no bound excited states. As the 9Be has no bound excited states
either, we concluded that those events should correspond to 9Be breakup. Another possible expla-
nation to the inelastic events in the 6He line would be the presence of multiple-scattering in the 9Be
target as the 6He goes through it. The 9Be target is rather thick, 1020 particles/cm2 in comparison to
the 1018 particles/cm2 of the Gold target. However, inspection of the scattering probability, using the
6He+9Be Rutherford cross section for those scattering angles and the target thickness, gives an scat-
tering probability of the order of 10−6 which would lead to 10−12 for double scattering which looks
too small to affect our measurements.
A preliminary analyses for the angular distributions of the target breakup events shows cross
sections ranging from 100 − 10 mb in the angular range from 20 − 60 degrees, which is a rather high
cross section. Coupled Channel calculations for the 9Be excitation of the two excited states (5/2−;
E=2.43 MeV) and (7/2−; E=6.38 MeV), assuming a collective model account for about only 1/5 of
the measured cross sections.
3 Summary and Conclusions
Experimental data for 6He+9Be, measured at 16.2 and 21.3 MeV using the RIBRAS facility, are
presented. The angular distributions for the elastic scattering have been analysed in terms of the CC,
3b- and 4b-CDCC methods considering the projectile breakup [6].
A large yield of α-particles has been observed in the spectra obtained with the 9Be target, indi-
cating a large reaction cross section. However, due to the presence of beam contaminants, it is not
possible to conclude that those α-particles are produced only in reactions induced by the 6He beam.
Probably, the beam contaminants, mainly 7Li and α-particles, are playing a role in the total α-particle
production cross section.
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Events of 6He particles scattered with lower energy than the elastic peak have been measured
and are related to the target breakup. Very high cross sections have been observed indicating that
target breakup may give an important contribution to the total reaction cross section in the 6He+9Be
collision.
4 Acknowledgments
The authors acknowledge the Fundação de Amparo à Pesquisa no Estado de São Paulo and Fundação
Araucária for the financial support.
References
[1] P.N de Faria and et al, Phys. Rev. C 81, 044605 (2010).
[2] E.F. Aguilera and et al., Phys. Rev. C 83, 021601(R) (2011).
[3] K. Rusek and et al., Phys. Rev. C 72, 037603 (2005).
[4] P.N. de Faria and et al., Phys. Rev. C 82, 034602 (2010).
[5] A.M. Sánchez-Benítez and et al., Nuclear Physics A 803, 30 (2008).
[6] K.C.C. Pires and et al., Phys. Rev. C 83, 64603 (2011).
[7] R. Lichtenthäler and et al., Eur. Phys. Jour. A 25: 259-260, Suppl. 1 (2005).
[8] A.M. Moro and et al. Phys. Rev. C 75(6), 064607 (2007).
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Study of reactions induced by 6He on 9Be

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Study of reactions induced by 6He on 9Be

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