Dynamic s udies o 11Li and i s co e 9Li on 208Pb
nea he Coulomb ba ie
M. Cube o1, M.J.G. Bo ge1, L. Acos a2, M. Alco a1, M.A.G. Al a ez5,6,
C. Dige 3, D. Gala iz4, J.P. Fe nández-Ga cía5, J. Gomez-Camacho5,6, J.A.
Lay5, M. Madu ga1, I. Ma el2, A.M. Mo o 5, I. Mukha5, A.M. Sánchez-
Bení ez2, A. Sho e 7, O. Tengblad1, P. Walden7.
1 Ins . Es uc u a de la Ma e ia, CSIC, Se ano 113bis, E28006 Mad id, Spain.
2 Depa amen o de Física Aplicada, Uni e sidad de Huel a, E-21071, Huel a, España
3 Depa men o Physics, Uni e si y o Yo k, Yo k, UK
4 CFNUL, Uni e sidade de Lisboa, A . P o . Gama Pin o 2, 1649-003, Lisboa, Po ugal
5 Depa amen o de FAMN, Uni e sidad de Se illa, E-41080 Se illa, España
6 Cen o Nacional de Acele ado es, Uni e sidad de Se illa-Jun a de Andalucía-CSIC, A . Thomas A.
Edison, 41092 Se illa, España
7 TRIUMF, Vancou e , B i ish Columbia, Canada, V6T 2A3
* email: mcube [email protected] mac.csic.es
Abs ac . We measu ed he sca e ing o he halo nucleus 11Li and i s co e 9Li on he lead a ge
a TRIUMF a ene gies below and a ound o he Coulomb ba ie . We epo he e on ou
p elimina y analysis o he inclusi e b eakup eac ion.
Keywo ds: Halo nuclei, 11Li, 9Li, Elas ic sca e ing, B eakup channel.
PACS: 25.70.Bc; 25.60.Dz; 25.60.Gc; 25.60.Bx; 21.10.G ; 27.20.+n
INTRODUCTION
In he pas 20 yea s he e has been an in e es in he nuclea physics communi y o
s udy he halo s uc u e. 11Li is he a che ype halo nucleus composed o a 9Li co e and
wo neu ons wi h e y low binding ene gy (S2n=369.15 (65) keV [1]). Recen
heo e ical calcula ions p edic ed a de ia ion om he s anda d elas ic c oss-sec ion o
s able nuclei, due o he dis o ion o he wa e unc ion o his loosely bound sys em
when passing nea a s ong Coulomb ield.
To s udy his e ec an expe imen o measu e he elas ic and b eakup c oss-sec ions
o 11Li on 208Pb a ene gies below and a ound he Coulomb ba ie was pe o med in
ISAC II (Iso ope Sepa a o and Accele a o ) a TRIUMF labo a o y in Vancou e ,
Canada.
Bo h 11Li and 9Li we e measu ed wi h he same cen e o mass ene gies using he
same se up. This will help us disen angle he con ibu ion o he 11Li halo o he p ocess
and o p ecisely de e mine he op ical model pa ame e s desc ibing he sca e ing
p ocess.
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CP1231, La Rábida 2009, In e na ional Scien i ic Mee ing on Nuclea Physics, Basic Concep s in
Nuclea Physics: Theo y, Expe imen s, and Applica ions, edi ed by J. A. Caballe o, C. E. Alonso, M. V. And és,
J. E. Ga cía-Ramos, and F. Pé ez-Be nal © 2010 Ame ican Ins i u e o Physics 978-0-7354-0776-3/10/$30.00
EXPERIMENTAL SET-UP AND DATA ANALISIS
We used a se o ou elescopes wi h angula co e age om 10º o 140º. The o wa d
elescopes consis ed o 40 μm DSSSD (Double Side Silicon S ip De ec o ) backed by a
500 μm Silicon PAD. The backwa d elescopes ha e a e y hin 20 μm SSSD (Single
Side Silicon S ip De ec o ) backed by a 60 μm DSSSD o sepa a e he con ibu ion o
he elas ic 11Li and b eakup, 9Li nuclei. See igu e 1.
We selec ed he doubly magic nucleus, 208Pb, as a a ge o a oid any ex a e ec
con ibu ing o he b eakup p ocess. The a ge hickness chosen was 1.45 mg·cm-2 as a
comp omise be ween su icien s a is ics and ex a b oadening due o he s aggling. The
a ge was a 15º wi h espec o he beam in o de o a oid shadowing om he a ge
ame on he de ec o .
(a) (b)
FIGURE 1. Expe imen al se -up and pixel-by-pixel analysis. (a) A is ic iew o he se up. The pola
angle dis ibu ion is shown on he DSSSD. (b) The pic u e displays he bi-dimensional plo ∆E e sus
∆E+E o he sca e ing e en s o he 11Li beam on 208Pb a 2.2 MeV·u-1 o he angula ange 20º o 35º.
We measu ed 9Li beam a 2.67 and 3.27 MeV·u−1 ene gies o a o al o 19h wi h he
1.45 mg·cm−2 a ge o 208Pb. In o de o selec he op imal hickness o he a ge and o
cha ac e ize he op ical po en ial we s udied 9Li a 3.27 and 3.67 MeV·u−1 wi h a a ge
o 1.9 mg ·cm−2 du ing 41.5h. A e wa ds we s udied 11Li a 2.2 and 2.7 MeV·u−1 du ing
abou 100h wi h he a ge o 1.45 mg·cm−2. Du ing he expe imen he de ec o s we e
calib a ed wi h he s anda d α-sou ces 148Gd, 239Pu, 241Am and 244Cm.
In he da a analysis se e al condi ions we e used. (i) Ene gy h esholds we e
de e mined om he α-sou ces. (ii) The di e ence be ween he ene gy in on and back
s ips is less han 70 keV so ha mul i-sca e ing om ligh pa icles like be as as well
as cha ge sha ing be ween s ips was a oided.
Figu e 1 (b) shows he elas ic and b eakup e en s o 11Li a ene gies well below he
Coulomb ba ie . The conside able amoun o b eakup e en s obse ed a hese close o
o wa d angles indica es ha he e ec on he sca e ing p ocess o he loosely bound
s uc u e o 11Li is highe han expec ed.
REFERENCES
1. M. Smi h e al., Phys. Re . Le . 101, 202501 (2008).
2. A. Mo o e al., Phys. Re . C 75, 064607 (2007).
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