Transfer to bound and unbound states in Exotic Nuclei around N16

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Transfer to bound and unbound states in Exotic
Nuclei around N16

• B. Fernández-Domínguez
• (University of Liverpool)

• Physics Motivation N16 region
• Experimental technique Ex20O(d,p)21O
  
• Preliminary Results

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Physics Motivation Shell evolution with isospin
Experimental evidences on the structure of n-rich
nuclei show a change in the magic numbers
sequence N8, N20, (N14,16) Theoretically the
nuclear shell model based on the mean-field
picture can no longer reproduce the shell
structure of exotic nuclei
New terms become important in the description of
the nucleus -variation of nuclear mean field
with neutron excess due to tensor
interactions -importance of many body
correlations -influence of open channels on
weakly bound and unbound states
New data on exotic nuclei with long isotopic
chains are very important. Single-particle
states.
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N16 region
N16 magic number for large isospin
The d3/2 level responsible for the
N16 shell gap
A. Ozawa et al. Phys. Rev. Lett.84 (2000) 5493.
Tz
Tz
Locate the d3/2 single-particle orbital in n-rich
oxygen isotopes
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n-rich oxygen isotopes
n-drip line just known for the ligth nuclei up to
oxygen
Wealth of measurements in the N14 N16 shell
gap
Z8
-Knockout reactions at GSI and MSU D. Cortina et
al et al PRL 98, 102502(2007) Spin and parity of
ground state of 23O A. Schiller et al. PRL
99,112501(2007)
N16
N14
-In-beam gamma-ray spectroscopy for O-isotopes
A20 to 24. M. Staniou et al. Phys. Rev. C69,
034312 (2004) 24O,23O not bound excited states-gt
threshold in the N16 strength 22O measure the
Ex(2)-gtsignature of N14
Population of 5/2 hole state in 23O
-Single-neutron tranfer 22O(d,p)23O-gt22On Z.
Elekes et al PRL 98, 102502(2007) Single-particle
d3/2 state and SF Strength of the N16 shell gap

-Inelastic scattering P. G. Thirolf et al. PLB
485(2000) 16-22 22O Ex(2)/B(E2) -gtevidence of
N14 shell gap
-Proton elastic and Inelastic scattering
22O(p,p) E. Becheva et al. PRL 96,
012501(2006) Disentangles p-n contrib to the 2
excitation in 22O -gtevidence of N14 shell gap
Study single particle structure of 21O via
20O(d,p)21O
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Previous measurements
21O
21O
d3/2 ?
21O In beam fragmentation ?-ray spectroscopy M.
Staniou et al. Phys. Rev. C69, 034312 (2004)
18O(18O,15O)21O multinucleon transfer W. Catford
et al., Nuc. Phys. A 503, 263 (1989)
d3/2 single-particle orbital has not been found.
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AIM OF THE EXPERIMENT
Measure for the first time -Excitation energy
and Spectroscopic factor (SF) of the so-far
unobserved 3/2 state -SF of the bound states
18O(d,p)19O
20O(d,p)21O
Experimental values
Ex
Predicted values (USD)

• Clear signature of three strong single-particle
  states ( d5/2 , s1/2 , d3/2) in 21O
• Some population of 3/2- perhaps possible

Unbound state above the n-threshold
Sn3.8 MeV
Spectroscopy of Bound-Unbound states Ex,Jp,
Spectroscopic Factors (SF)
Particle spectroscopy technique through (d,p)
reaction
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Direct Reactions (d,p) probe
Spectroscopy of Bound-Unbound states Ex,Jp,
Spectroscopic Factors (SF)
Measurements -gt Observables Invariant mass
method -gt reconstruct the decay energy 20On ?p
-gt ds/d? -gt (l , SF)
Measurements -gt Observables Ep and/or E? -gtEx ?p
-gt ds/d? -gt (l , SF)
Inverse kinematics-gt(d,p),(d,t),(d,3He),(d,d)
Elastic scattering DWBA fix optical potentials
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Inverse Kinematics 20O d _at_ 10.9 AMeV
Light ejectile -gt charged-particle array

• Kinematics compression -gtEp good resolution
• States separated by 1 MeV -gt200 keV in Ep
• Covers large range in ?lab -gt4? ang cover
• Deposit of low Energy-gtThreshold problems

Heavy recoil -gt spectrometer
Dp/p10

• Angular acceptance (VAMOS ? 7 ?)
• Momentum acceptance (VAMOS ? 5)

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Experimental Set-Up
TIARAMUST2
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PRELIMINARY ANALYSIS d(20O,p)21O ? 21O ?
(bound states)
Preliminary (on-line results) 40 data
TIARA
21O
20O
19O
VAMOS
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PRELIMINARY ANALYSIS d(20O,p)21O ? 20O n
(unbound state)
Preliminary (on-line results)
VAMOS
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PRELIMINARY ANALYSIS d(20O,d)20O ? 20O d
Preliminary (on-line results)
VAMOS
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SUMMARY

• Online analysis of the experiment confirms we
  can study different reactions channels, obtain
  level energies and l-values information
• transfer to bound and unbound states with full
  channel identification
• triple coincidences with excellent gamma energy
  resolution
• also have (d,d) and (d,t) acquired
  simultaneously with TIARA and MUST2

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TIARAMUST2VAMOSEXOGAM Collaboration
J. S. Thomas, S.M. Brown, W.N. Catford, N.P.
Patterson, G.L. Wilson University of Surrey
M. Chartier, B. Pietras University of Liverpool
M. Labiche, R.C. Lemmon STFC Daresbury
G. de France, F. Delaunay, C. Force, A. Navin, M.
Rejmund, O. Sorlin GANIL
D. Beaumel, Y. Blumenfeld, N. de Séréville, S.
Franchoo, J. Guillot, F. Hammache, F. Maréchal,
B. Mouginot, A. Ramus, J-A. Scarpaci, J. Stefan
IPN Orsay
N.L. Achouri, H. Al Falou, A. Leprince, N.A. Orr
LPC Caen
V. Lapoux, B. Martin, X. Mougeot, L. Nalpas, E.C.
Pollaco CEA Saclay
N.I. Ashwood, N. Curtis, P. Haigh University of
Birmingham
R. Chapman University of the West of Scotland
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No part of the talk

• Open quantum systems 2008

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TIARA-MUST2 CAMPAIGN AT SPIRAL/GANIL to study the
N16 shell gap

• E522s Single-Particle Energies in Neutron-Rich
  Oxygen Isotopes
• E445s Changing shell structure near N16 probed
  by (d,p) on Ne isotopes