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Study of high lying resonances in 9Be by the measurement of (p,p), (p,d) and

(p,α) reactions

Alinka Lépine-Szily, and the RIBRAS collaboration

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Tandem Accelerator – Pelletron 8UD at the University of São Paulo - Brazil

3.0 – 5.0 MeV/nucleon

primary beams:6,7Li, 10,11B, 9Be,12C, 16,17,18O ...

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RIBRAS - Radioactive Ion Beams in Brazil First RIB facility in the Southern Hemisphere,installed in 2004

Two superconducting solenoids: in-flight radioactive ion beam production :

Solenoid -1 Solenoid - 2

Degrader in first scattering chamber

Target Detectors 3 new strip-detector telescopes

( ) 22

qAEkB =ρ

E

ΔE

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q  Max field 6.5 Tesla q  versatile configuration q  persistent mode q  low LHe and LN2 consumption

6He,8Li,7Be,8B,10Be,17F Typical intensities: 104 - 106 pps

Evolution of the RIBRAS system Cocktail beams

Purified beams

New chamber for γ-detectors, on-line fusion measurements

Neutron Wall

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6He borromean , two- neutron halo nucleus

What is the interest of these light radioactive nuclei??

Measurements with purified radioactive beams:

Elastic scattering and transfer reactions

of 8Li on hydrogen target

Nuclear states with excited cores and with cluster structures: 2,3..

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𝐸↓𝑐𝑚  7Li+d

α+α+n

8Li+p

•  Probes 9Be around 𝐸↓𝑥 ≈18−20 MeV •  High excitation energies in 9Be

à unknown states à level density important à several open channels

Study of 9Be structure through 8Li+p reactions

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Method: Inverse kinematics: 8Li beam hitting a thick (7.7 mg/cm2) [CH2]n target 8Li beam looses energy, stops in the target

8Li beam

E1 E2

Si-telescope 4He,p,d,t

∫Δ+

Δ−=

2/

2/,;

)()()()(

EE

EE ii

i dEEEEIEY

εσ

ε = stopping power

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Simultaneous measurement of all incident energies: excitation function Resonances populated in the target àpeaks in energy spectrum of light ejectiles. Energy spectrum of 4He, p, d à excitation function of reactions Energy resolution: independent of beam dispersion, depends on energy loss of light ejectiles in target Normalization; Rutherford scattering of 8Li on Au target

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2009-2011 8Li(p,α) 5He, one solenoid, Q=+14.42 MeV,

Ecm

Subtraction of α contribution 5Hegs à α +n 5He*à α +n Phase space 9Beà α+ α+n

8Li(p,α)5He

10

ΔE (MeV)

2013 – 2015 – 2 solenoids--purified 8Li beam θlab= 10 and 18º

E+ΔΕ(MeV)

protons deuterons tritons

alphas t d p

E+ΔΕ(MeV)

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Ep (MeV 0

10

20

30

40

50

60

70

1.00 1.20 1.40 1.60 1.80 2.00

8Li(p,p)8Li at 18o

Ecm (MeV)

8Li(p,α)5He at 13,5o

Broad resonance at Ecm~1.7MeV, observed in (p,α) and (p,p). In (p,d) it populates both 7Ligs and 7Li*(0.477 MeV).

Ecm (MeV)

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0.0

10.0

20.0

30.0

40.0

50.0

4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0

8Li(p,d)7Li 10o

0.0

10.0

20.0

30.0

40.0

50.0

15.0 20.0 25.0 30.0 35.0

8Li(p,α)5He 10º

0.0

10.0

20.0

30.0

40.0

50.0

60.0

5.5 6 6.5 7 7.5 8 8.5 9 Ed(MeV)

8Li(p,d)7Li 18o

0.0

10.0

20.0

30.0

40.0

50.0

19.0 21.0 23.0 25.0 27.0 29.0 31.0

8Li(p,α)5He 18 o

Eα (MeV)

7Li* 7Li gs

The resonance at Ecm ~ 1.7 MeV decays to d + 7Ligs and 7Li* (0,477MeV). At 10º the peak of d + 7Ligs was covered by a contamination

Ed (MeV)

Eα (MeV)

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R-matrix calculation Procedure: 1.  Inputs for each resonance: 𝐽,𝐼,ℓ, 𝐸↓0 , 𝛾↓𝑝 , 𝛾↓𝛼 , 𝛾↓𝑑  2.  Calculation of the R-matrix for each J values 3.  From R-matrices: calculation of the scattering matrices UJ for each J 4.  From the scattering matrices UJ : elastic and transfer cross sections

Several reactions with the same entrance channel à constrains Energy 𝐸↓0 , proton width 𝛾↓𝑝  are common à constrains

8Li(p,p)8Li: 𝑅↓𝑝𝑝 (𝐸)= 𝛾↓𝑝↑2 /𝐸↓0 −𝐸  8Li(p,α)5He: 𝑅↓𝑝𝛼 (𝐸)= 𝛾↓𝑝 𝛾↓𝛼 /𝐸↓0 −𝐸  8Li(p,d)7Li: 𝑅↓𝑝𝑑 (𝐸)= 𝛾↓𝑝 𝛾↓𝑑 /𝐸↓0 −𝐸 

5-channels: 8Li + p 5He + α 5He*(1/2-)+ α 7Ligs + d 7Li* (1/2-) + d 13

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0.0

50.0

5.00 6.00 7.00 8.00 9.00Ed(MeV)

8Li(p,d)θlab=18o

0.0

10.0

20.0

30.0

40.0

50.0

4.00 5.00 6.00 7.00 8.00 9.00

8Li(p,d)7Liθlab=10o10o

Ed(MeV)

contam

inaA

on

0.0

10.0

20.0

30.0

40.0

15.0 19.0 23.0 27.0 31.0 35.0

8Li(p,α)θlab=13,5o

Eα(MeV)

1.66+1.72MeV

0.0

10.0

20.0

30.0

40.0

15.0 19.0 23.0 27.0 31.0 35.0Eα(MeV)

8Li(p,α)θlab=10o

0.0

50.0

100.0

1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2

8Li(p,p)8Liθlab=18o

R-matrix fits: 5 resonances at 0.42, 0.61, 1.10, 1.66 and 1.72 MeV. At 1.66 broad state (Γp, Γα ∼200 keV, , Γd ∼100 keV) At 1.72 MeV narrower state (Γp, Γα ∼ 50 keV, , Γd’ ∼ 100 keV)

deuteron channel: large reduced width à  Strong 7Li+d structure à  State with excited core à  α+t+p+n four-body state

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Ecm (MeV)

d=p+n

Multi-channel R-matrix fits to the data (5-channels)

0.0

10.0

20.0

30.0

40.0

18.0 20.0 22.0 24.0 26.0 28.0 30.0 32.0

8Li(p,α)θlab=18o

Eα(MeV)

1.66 + 1.72MeV

7Li=α + t

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0.0

20.0

40.0

5.00 6.00 7.00 8.00 9.00Ed(MeV)

8Li(p,d)θlab=18o

0.0

20.0

40.0

5.00 6.00 7.00 8.00 9.00Ed(MeV)

8Li(p,d)θlab=18o

0.0

20.0

40.0

12.5 17.5 22.5 27.5 32.5

8Li(p,α)θlab=13,5o

Eα(MeV)

2 resonances close: at 1,66 and 1,72 MeV

E R Jπ Γp Γα Γd Γd’ 1.66 7/2- 0,26 0,18 0,10 0,04 1.72 5/2- 0,06 0,03 0,04 0,1

E R Jπ Γp Γα Γd Γd’

1,72 5/2- 0,06 0,03 0,04 0,1

Γα Γα

E R Jπ Γp Γα Γd Γd’ 1,66 7/2- 0,26 0,18 0,10 0,04 Γα

1 resonance only

0.0

10.0

20.0

30.0

40.0

5.00 6.00 7.00 8.00 9.00Ed(MeV)

8Li(p,d)θlab=18o

0.0

20.0

40.0

12.5 17.5 22.5 27.5 32.5

8Li(p,α)θlab=13,5o

Eα(MeV)

Conclusion: need for 2 resonances to reproduce the separation of peaks in (p,d)

or

Conclusions •  The simultaneous measurement of resonant elastic scattering

8Li(p,p)8Li, and transfer reactions 8Li(p,α)5He and 8Li(p,d)7Li, allows to determine the resonance parameters of highly excited states in 9Be.

•  5 resonances, at Ecm= at 0.42, 0.61, 1.10,1.66 and 1.72 MeV have ER, Jπ and partial widths Γp, Γα, Γd, Γd’ determined

•  Future measurements: extend the energy range and measure angular distributions

•  Study other systems 6He+p, 8B+p, 7Be+p 16

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RIBRAS COLLABORATION Universidade de São Paulo, IFUSP R. Lichtenthäler Fo, A. Lépine-Szily, V.Guimarães, M. A. Gonzalez Alvarez, K.C.C. Pires, V.Scarduelli, E.Leistenschneider, S. Appannababu, L.Gasques, G. A. Scotton, U. U. da Silva Université Libre de Bruxelles P. Descouvemont Universidad de Sevilla, Espanha M. Rodríguez-Gallardo, A.M. Moro Laboratorio Tandar, Buenos Aires, Argentina A. Arazi CEADEN, Havana, Cuba I.Padron, Instituto de Pesquisas Energeticas e Nucleares (IPEN) J.M.B. Shorto Universidade Federal Fluminense (UFF) P.R.S. Gomes, J. Lubian, P. N. de Faria, D. R. Mendes, R. Pampa Condori, M.C. Morais Universidade Federal de São Paulo (UNIFESP) M. Assunção Universidade Federal Rural do Rio de Janeiro (UFRRJ) V. Morcelle Universidade Federal da Bahia (UFBA) A. Barioni University of Notre Dame, EUA J. Kolata Faculty of Science, The M.S. University of Baroda, India Surjit Mukherjee

In memoriam of our dear colleague and friend Paulo Gomes. Rest in peace

18 ~1980 2015