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Structure of Light Neutron- Rich Nuclei via Breakup and Transfer

Structure of Light Neutron- Rich Nuclei via Breakup and Transfer. Preamble N=7 structure beyond the neutron dripline via knockout and fragmentation of fast secondary fragmentation beams N=16  20 intruder states via single- nucleon transfer with a reaccelerated ISOL beam

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Structure of Light Neutron- Rich Nuclei via Breakup and Transfer

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  1. Structure of Light Neutron-RichNucleivia Breakup and Transfer Preamble N=7 structure beyond the neutron dripline via knockout and fragmentation of fast secondary fragmentation beams N=1620 intruder states via single-nucleontransferwith a reaccelerated ISOL beam Conclusions & Perspectives Nigel Orr LPC-Caen, France CHARISSA+DEMON & TiaRA Collaborations ‟Formless Continuum” – Jack Haas

  2. How to explore experimentallyshell structure as the (neutron) driplineisapproached ? … KoRIA→Fast fragmentation beams (~100 MeV/nucleon) Post-accelerated ISOL beams (~10 MeV/nucleon) ISOL  nucleontransfer Frag breakup, knockout, …

  3. N=7 : Structural Evolution with Isospin* … … 10Li &9He ?? PG Hansen et al. T Otsuka et al. PRL 2001 1/2+- 1/2-level inversion … * Also input for 3-body models of 11Li, …

  4. Strategy … Removal of nucleon(s) fromhigh-energysecondarybeam  highs, thicktarget, forwardfocussing …[ → Valence (halo) neutron removalfromBorromean projectile[ -1n ] ]→ Proton removalfromlessexotic projectile (known structure)[ -xp ]→ “Fragmentation” of projectile– typically p removalfollowed by n-decay[ -xp-yn ]  systemsbeyonddripline – observe frag.+ n FSI

  5. Vf Vf - Vn Vn Proj. target AZ A-1Z + n Experimental Approach … … nucleonremoval via “knockout” or breakupof projectile (b 0.3) withknown structure + in-flight decay  fragment – n FSI

  6. Approx. “SelectionRules” … (i) 1 & 2-proton knockout  Dℓn0 proj. valence neutron config.C(11Be,9Li+n)X ,C(11Be,8He+n)X s1/2 [ 11Be C2S (s1/2) 0.8 ]C(14B,12Be+n)X  s1/2 +d5/2 [ 14B C2S (s1/2)+ C2S (d5/2) 1.0 ]welladapted to probinglow-lying s-wavestrength(ii) fragmentation (-xp,-yn)  population via neutron-decay of N+1 system C(14B,9Li+n)X , C(14B,8He+n)X, C(14B, 9Li+n)X  s1/2 + p1/2 + …CAVEAT: decay of narrowresonances in N+1,2,… systems

  7. Scattering/Virtual s-wave States … as = 0 fm no FSI ; as << 0 fm stronger FSI NB:final lineshape Ed(frag+n) depends on projectile and reaction + decay path

  8. 10Li: C(11Be,9Li+n) @ 35 MeV/nucleon [-1p] s-wave [as = -17±2 fm] + non-resonant continuum H Al Falouet al., 2011

  9. 10Li: C(14B,9Li+n) @ 35 MeV/nucleon [-2p,-2n] s-wave [as = -10±2 fm] + p-wave [Er = 0.50, G0 0.50 MeV] + background [ Decay of 11Li* & 12Li … ? ] H Al Falouet al., 2011

  10. 9He: C(11Be,8He+n) @ 35 MeV/nucleon [-2p] s-wave [as = -3 ~ 0 fm (3s)] + non-resonantcontinuum H Al Falouet al., 2011

  11. 9He: C(14B,8He+n) @ 35 MeV/nucleon [-3p,-2n] s-wave [as= -3 ~ 0 fm] + p-wave [Er = 1.2, G0 1.0 MeV] + background [ Decay of 10He & 11He … ? ] H Al Falouet al., 2011

  12. 9He: p(11Li,8He+n) @ 280 MeV/nucleon [-1p-1n] GSI-LAND : HT Johansson, Yu. Aksyutina et al. (2010)

  13. Conclusions N=7… “Spectroscopy” of neutron unboundsystems possible via nucleon knockout & fragmentation fromfast RNB …10Li : low-lying s-wavestrength (as ~ -15 fm) low-lying p-waveresonance (Er = 0.5 MeV)  N= 7 1/2+ - 1/2- inversion confirmed… but pp3/2ns1/2 ,np1/2 ,nd5/2 ? 9He : low-lying s-wavestrength (as  3 fm) + Ex1.2 MeV + ... (ℓ>0) … FSI << 9Li+n ? Is this9He or … ? … Try d(8He,p)9He THEORY:realisticstructure + reactionmodellingneeded (lineshape and crosssection) including non-resonant continuum + …

  14. Shell structure in ‟heavier” neutron-richnuclei … … A~30 : behaviour of nd5/2,ns1/2,nd3/2np3/2,nf7/2 orbitals  N=14, 16, 20 gaps N=20 dripline stable MCSM [SDPF–M] : Utsunoet al. (1999)

  15. Low-lyingnfpintruder states in 27Ne … N=17 • … N=17isotones systematics • rapidlowering of nfp states for Z<14 • and 3/2- -7/2- inversion ? 27Ne: nfp states SM predictions verydifferent … Expt: 3/2- tentativelyassigned 7/2- ?? … S Brown, PhDThesis (2011) ( )

  16. Probe single-particlestrength via neutron-transfer onto 26Ne: d(26Ne,p)27Ne … … Measure proton energy and angle in coincidencewithheavyresidue … (d,p) inverse kinematics  qlab (proton) ~ 60-180 ° ℓn=0 1 2 3 S Brown, PhDThesis (2011) d(26Ne,p)27Ne : ds/dW (lab) ℓn

  17. 27Ne bound-states: d(26Ne,pg)27Ne … … select boundexcited states usingg-rays 3/2 ℓn=1 3/2+ ℓn=2 C2S = 0.64(33)* C2S = 0.44(22)* Ex=765 keV g.s. * ADWA calculations ofds/dW S Brown, PhDThesis (2011)

  18. 27Ne unbound-states: d(26Ne,p)26Ne … … strongn1f7/2levelunbound (~0.3 MeV) lies ~1 MeV above n2p3/2 level Ex=1.74 MeV Ex=1.74 (9) MeV C2S = 0.35(10)* … * ADWA calculations ofds/dW S Brown, WN Catford et al., (2011)

  19. Low-lyingnfpintruder states in 27Ne … …‟WBP-M” nfpshell lowered (-0.7 MeV*) *WBP-M : 25Ne & 29Mg well reproduced S Brown, WN Catford et al., (2011)

  20. Conclusions d(26Ne,p)… Neutron transfer in inverse kinematics map single-particle strength direct probe of evolution of energies of orbitals  27Ne: n1f7/2levellocated as a resonancesome1 MeV above n2p3/2 level WBP-M : reproduce Ex (and C2S) with an ad hoc lowering of nfp orbitals (N=20 gap) by 0.7 MeV …  THEORY:coherent description of 27Ne and neighbouringnucleiwithout introduction of any ad-hoc changes … influence of continuum ??

  21. Perspectives: KoRIA … … BeamsenvisagedatKoRIAwellsuited to direct reaction studies of structure far fromstability Fast Fragmentation beams (EB>30 MeV/u) → knockout, breakup, … spectrometer, sweeper, g-array, neutron array (Xn) …  ISOL (EB~5-10 MeV/u) →transfer (d,p), (d,t), (d,n), …  4p Si-strip array (active target ?), g-array, large acceptance spectrometer [heavy residue ID], low-energy n-array, …

  22. New comers to fieldverywelcome … a way to make contacts !

  23. WBP-M*: Low-lyingnfpintruder states in 25,27Ne & 29Mg … *nfpshelllowered : -1.0 MeV S Brown, WN Catfordet al., (2011)

  24. 9He : d(8He,p) @ 25 MeV/nucleon → MS Golovkov et al., PRC76 (2007)

  25. 9He : d(8He,p) @ 15.4 MeV/nucleon MUST2: T Al Kalanee, J Gibelin et al. (2012), T Al Kalanee LPCC T-10-02

  26. 10Li:p,C(11Li,9Li+n) @ 300 MeV/nucleon [-1n “knockout”] H Simon et al. NUPA (2007) ; Yu. Aksyutina PLB (2008)

  27. 10Li :C(11Li,9Li+n) AngularCorrelations … 11Li n1 10Li n2 9Li H Simon et al. NUPA (2007)

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