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Reaction experiments induced by light exotic nuclei at REX-ISOLDE

Reaction experiments induced by light exotic nuclei at REX-ISOLDE. Olof TENGBLAD Instituto de Estructura de la Materia Consejo Superior de Investigaciones Científicas Madrid Spain. Madrid-Aarhus- Göteborg. Probing the halo @ REX

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Reaction experiments induced by light exotic nuclei at REX-ISOLDE

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  1. Reaction experiments induced by light exotic nuclei at REX-ISOLDE Olof TENGBLAD Instituto de Estructura de la Materia Consejo Superior de InvestigacionesCientíficas Madrid Spain Madrid-Aarhus-Göteborg

  2. Probing the halo @ REX IS367 P100 Study of the unbound nuclei 10Li and 7He at REX ISOLDE IS371 P105 Investigations of neutron-rich nuclei at the dripline through their analogue states: The cases of 10Li-10Be (T=2) and 17C-17N (T=5/2) IS399 P134 Exploring the dipole polarizability of 11Li at REX-ISOLDE IS430 P187 Study of neutron-rich Be isotopes with REX-ISOLDE The first run took place September 2005. Beam energy 2.25 MeV/u, thin stripper foil to reduce the amount of 22Ne. Two DSSSD (32 by 32 strips) backed by 1.5 mm Si in the forward direction, monitor telescope in beam dump behind reduction foil. Targets: deuterated polyethylene and standard polyethylene, Ag for normalization. The second run took place October 2009. The MINIBALL with the T-REX chamber were used. Beam energy 2.85 MeV/u. Targets: Deuterated polyethylene, polyethylene, Ag, carbon and aluminum. The third run (remaining 18 shifts) took place September 2010. Same configuration, beam energy and targets as October 2009. Mainly runs with 15 mm collimator, a few with 5 mm. IS438 P192 Elastic scattering and fusion studies in the reactions 10,11Be+64Zn A. Di Pietro, Catania IS444 P206 Exploring halo effects in the scattering of 11Be on heavy targets at REX-ISOLDE IS446 P211 Investigation of the 8Li(2H,p)9Li reaction at REX-ISOLDE

  3. Bound lithium isotopes Stable T1/2= 836 ms 178ms 8.5 ms 8Li 6Li 7Li 9Li 11Li – a halo nucleus nuclear radius (fm) Brief11Li History 1966 foundbound 1975 1st spectroscopy C. Thibault @ CERN PS ISOLDE intense studydifferentdecaymodes n,2n,3n,t etc 1985 Tanhihata Berkeley exp 11Li ishuge! 1987 PG Hansen & B. Jonson 9Li core+ 2n halo mass number

  4. Purpose: Study the structure of neutron-rich lithium isotopes using transfer reactions. Goal: Reaction cross-sections compared with theoretical models, spectroscopic factors. Neutron-rich lithium isotopes X X X X X Debated

  5. IS371 T=2 T=1 Probing unbound 10Li @ REX IS371 Elasticresonancescatteringtoinvestigate E, J of lowestT=2states in 10Be analoguesof gs and 1:st excitedstate of 10Li IS367 Transfer reactionat lowenergy s-wave pickup (d-target) p-wave pickup (Be-target) Characterizethegs and 1:st exitedstate of theunboundnucleus10Li 9Li d-polyethylen Post-accelerated 2.3 MeV/u 9Li beamfrom REX-ISOLDE on PE, d-PE, Be, target respectively.

  6. IS371:elasticresonancescattering9Li+1H ungated 600 ms BeamGate EBIS gated T1 Time arrival of event [ms] p < 600 ms Rutherford Bkg 600< p< 1200 ExcitationEnergy in 10Be [MeV] HIE ISOLDE with 5 MeV/u and ACTAR wouldhelptoimprove

  7. IS367: Nucelon transfer reaction: 9Li+2H/9Be Nuclear Physics A738(2004)511-514 Nuclear PhysicsA748(2005)374-392 Phys.Lett B635(2006)17-22 Phys.Lett B642(2006)449-454 d(9Li,10Li*)p using REX-ISOLDE 9Li+n

  8. Probing unbound 10Li @ REX 9Li (2x105 pps) @ 2.77 MeV/u proton-ion coincidences 8Li + t 9Li + d 10Li + p 9Li + d Cut-off [MeV] 11 6He 10 a 3.5 t 3.0 d 2.3 p -gs @ 25 keV , s1/2 (?) -1st excited @ 300 keV p1/2 -2nd state @ 500 keV, p1/2

  9. IS446: Nucelon transfer reaction: 8Li+2H ΔE-det. 32 x 32 strips 60 mm 2x2 mm2  < 3o resolution Maximize angular coverage Composition of the beam 8Li REX-ISOLDE beam @ 3.15 MeV/u: Reaction channels: 2H(8Li,p)9Li(*) – (d,p) pickup 2H(8Li,d)8Li(*) – (d,d) elastic 2H(8Li,t)7Li(*) – (d,t) stripping dσ/dΩ (a.u.) ΔE (MeV) a t p d E (MeV)

  10. Excitationenergyspectra Excitation-energies Elasticdeuteron Stripping triton Eex(8Li) Eex(7Li) dσ/dE (a.u.) dσ/dE (a.u.) E (MeV) E (MeV) Pickup proton Eex(9Li) dσ/dE (a.u.) E (MeV)

  11. Elastic scattering of 8Li (Jπ = 2+) Optical model (parameters for d(9Li,d)9Li) Compound contribution ~ 4 mb/sr Reasonable potential for inelastic and (d,p) channel. Inelastic scattering Coupled-channels Deformed Woods-Saxon potential deformation length 1.728 fm Theoretical calculations (FRESCO)A. Moro Sevilla P DWBA calculation (Distorted Wave BornAprox) Dpotentialbetween d & 8Li core Ppotential p & 8Li + n BBindingpotential8Li + picked up n D B

  12. Elastic/inelastic: 2H(8Li,d)8Li* Angular dependence of differential cross-section Joint analysis of elastic and inelastic channels Using DWBA and Coupled Channels CC methods The solid and dashed lines are the CC calculations with two different deuteron potentials. The dotted-dashed line is the CC calculation assuming a rotational model for the 8Li states, with an intrinsic quadrupole deformation length of 1.75fm. Works for elastic but failes the inelasticThe rotational description is inadequate to describe the coupling between 8Li states CoupleChannels DWBA CC calculations show betteragreementthan DWBA, whichconfirmstheimportance of higherordereffects

  13. Pickup: 2H(8Li,p)9Li* 9Li ground state – good agreement at small scattering angles where the cross-section for transfer reactions is largest. A two-step process improves the agreement in the interval 50-90°. Excited states in 9Li – the theoretical models give a lower reaction cross-section, can be due to compound nuclei, maybe excited states in 10Be (8Li + 2H → 10Be).

  14. Stripping: 2H(8Li,t)7Li* Measured angular distribution 2H(8Li,t) 7Li* cross section compared to; DWBA dashed line Coupled-Reaction-Channel CRC solid line The CRC calculation reproduce the data well Confirming the importance of multi-step process in this reaction. The overall result demonstrate that the transfer reaction remains a useful tool for investigating nuclear structure. Careful theoretical treatment is needed And more examples to tune the parameters on. The8li + 2H reaction at REX-ISOLDE E. Tengbornet.al. AcceptedPhysRev C (2011)

  15. Transfer reactions with 11Be • IS444 P206 Exploring halo effects in the scattering of 11Be on heavy targets at REX-ISOLDE  L. Acosta et.al. Eur. Phys. J. A 42, 461–464 (2009) • IS438 P192 Elastic scattering and fusion studies in the reactions 10,11Be+64Zn A. Di Pietroet.al. Phys. Rev. Let. 105, 022701, (2010) • IS430 P187 Study of neutron-rich Be isotopes with REX-ISOLDE Thesame set-up wasused at one time

  16. Transfer reactions with 11Be • Halo nucleus (also in bound excited state…) • Cluster structures in neighbours • N=8 broken in 12Be 12Be states • T. Aumann et al, PRL 84 (2000) 35 MSU, neutron-knockout • R. Palit et al, PRC 68 (2003) 034318 GSI, break-up and others… Knock out @ relativistic energies: 11Be to 10Be

  17. 11Be to 12Be R. Kanungo et al, PLB682 (10) 391 n-transfer at Triumf, 5 MeV/u Neutron knockout establishing N=8 breaking, e.g. A. Navin et al, PRL 85(00) 266; S.Pain et al, PRL 96 (06) 032502 RIKEN exps, excited states on 12Be: H. Iwasaki et al, PLB 481 (00) 7, 491 (00) 8; S. Shimoura et al, PLB 560 (03) 31; N. Imai et al, PLB 673 (09) 179 • Resolution for 10Be gamma-spectrum (preferential population to halo candidates 1- and 2- ??) • Separation of 12Be states, check spec. factors • Search for 0- excitation in 12Be What remains to do ? • IS430 P187 Study of neutron-rich Be isotopes with REX-ISOLDE • Sept. 2005 – 2ndbeamline • Oct. 2009 – T-REX (cut short, EBIS problems) • Sep. 2010 – T-REX (very successful run !!)

  18. 2005 run - results • Beam of 11Be, deuterium target, 2ndbeamline Comparison of differential cross sections for elastic scattering on deuteron for 11Be(Green) and 11B(Cyan), along with an optical model calculation for the latter(blackline). The curvatures of the two diferentialcrosssections are the same, but the one for 11Be is about a factor of three higher. A. Moro, calculation: optical potential

  19. 2010: Particle ID via DE-E 2010 improvedexperiment T-REX and MINIBALL set-up a t d p p d t T-REX detectors are toothick: 150 mm stops 16 MeVa no DE-E 2005 data

  20. Stripping: 11Be(d,t)10Be* 2+, 1-, 0+, 2- 2+ 0+ 2+to 2+ 2- to 2+ 2+ to 0+ 2+ 0+ 1- to 0+

  21. 10Be+t coincidencesi.e. complete kinematics θx versus θy

  22. Elastic/Inelastic:11Be(d,d)11Be* 320 keV

  23. Pickup: 11Be(d,p)12Be* Excitation spectra Black: Total Brown: Bg from reactions on C Red: 2+1 Green: 0+2 Blue: 1-1 . Gamma lines in coincidence with p. Purpel: The four above combined 511 line: 0+2 pair production Doppler corrected 2100: 2+12700: 1-1

  24. Gamma-gated 12Be spectra

  25. Cross sections from (d,p) Preliminary: Coupledchannelcalculations 0+1 gs 11Be(d,p)12Be 2+1 1-1

  26. Agreement between experimental data and theoretical calculations for (d,d) → the method describes the data. Good description of the ground state in 9Li → confidence to use the technique for more exotic nuclei where the nuclear structure is unknown. FUTURE Higher beam energy is needed HIE-ISOLDE. Zero degree Spectrometerwould help removing background and select channel Upgrade of T-REX with thinner detectors  lower alpha threshold ACTAR as a development of the elastic resonance scattering method Letter of Intentto HIE-ISOLDE Transfer reactions at and beyondthedripline tritiumtarget (t,p) t(9Li,p)11Lid(11Li,p)12Li t(11Li,p)13Li C-beams as next step Conclusions

  27. M. Alcorta1, M. Borge1, J. Byskov-Nielsen2, J. Cederkäll3, C. Diget2, L. Fraile1, H. Fynbo2, J. Gomez-Camacho4, H. Jeppesen2, H. Johansson5, B. Jonson5, O. Kirsebom2, H. Knudsen2, M. Madurga1, A. Moro4, T. Nilsson5, G. Nyman5, K. Riisager2, O. Tengblad1, E. Tengborn5, D. Voulot3, F. Wenander3 ISOLDE – REX – MiniBallcollaboration 1Institut Estructura de la Materia, CSIC, Spain 2Institut for Fysik og Astronomi, Aarhus Universitet, Denmark 3ISOLDE, PH Department, CERN Switzerland 4Departamento de FAMN, Universidad de Sevilla, Spain 5Fundamental fysik, Chalmers tekniska högskola, Sweden Core - Collaboration

  28. Thank you for your attention!

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