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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
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

slide2

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, …

n 7 structural evolution with isospin
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, …

strategy
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

experimental approach

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

approx selection rules
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

scattering virtual s wave states
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

10 li c 11 be 9 li n @ 35 mev nucleon 1p
10Li: C(11Be,9Li+n) @ 35 MeV/nucleon [-1p]

s-wave [as = -17±2 fm] + non-resonant continuum

H Al Falouet al., 2011

10 li c 14 b 9 li n @ 35 mev nucleon 2p 2n
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

9 he c 11 be 8 he n @ 35 mev nucleon 2p
9He: C(11Be,8He+n) @ 35 MeV/nucleon [-2p]

s-wave [as = -3 ~ 0 fm (3s)] + non-resonantcontinuum

H Al Falouet al., 2011

9 he c 14 b 8 he n @ 35 mev nucleon 3p 2n
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

9 he p 11 li 8 he n @ 280 mev nucleon 1p 1n
9He: p(11Li,8He+n) @ 280 MeV/nucleon [-1p-1n]

GSI-LAND : HT Johansson, Yu. Aksyutina et al. (2010)

conclusions n 7
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 + …

shell structure in heavier neutron rich nuclei
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)

low lying n fp intruder states in 27 ne
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)

( )

probe single particle strength via neutron transfer onto 26 ne d 26 ne p 27 ne
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

27 ne bound states d 26 ne p g 27 ne
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)

27 ne unbound states d 26 ne p 26 ne
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)

low lying n fp intruder states in 27 ne1
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)

conclusions d 26 ne p
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 ??

perspectives koria
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, …

slide24

WBP-M*: Low-lyingnfpintruder states in 25,27Ne & 29Mg …

*nfpshelllowered : -1.0 MeV

S Brown, WN Catfordet al., (2011)

slide25

9He : d(8He,p) @ 25 MeV/nucleon

MS Golovkov et al., PRC76 (2007)

slide26

9He : d(8He,p) @ 15.4 MeV/nucleon

MUST2: T Al Kalanee, J Gibelin et al. (2012), T Al Kalanee LPCC T-10-02

10 li p c 11 li 9 li n @ 300 mev nucleon 1n knockout
10Li:p,C(11Li,9Li+n) @ 300 MeV/nucleon [-1n “knockout”]

H Simon et al. NUPA (2007) ; Yu. Aksyutina PLB (2008)

10 li c 11 li 9 li n angular correlations
10Li :C(11Li,9Li+n) AngularCorrelations …

11Li

n1

10Li

n2

9Li

H Simon et al. NUPA (2007)