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Study of single particle properties of neutron-rich Na istopes on the „shore of the island of inversion“ by means of neutron-transfer reactions. Thorsten Kröll*. CERN-INTC-2009-037, INTC-P-272 . *TU Darmstadt – TU München – CERN – KU Leuven – Univ. Edinburgh

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Thorsten kr ll

Study of single particle properties of neutron-rich Na istopes on the „shore of the island of inversion“ by means of neutron-transfer reactions

Thorsten Kröll*

CERN-INTC-2009-037, INTC-P-272 

*TU Darmstadt – TU München – CERN – KU Leuven – Univ. Edinburgh

Chalmers TH Göteborg – Univ. West of Scotland, Paisley – IPN Orsay

LMU München – Univ. York – Univ. Manchester – Univ. Liverpool

Univ. Köln – CSNSM Orsay – Univ. Ioannina – IRNRE Sofia

Univ. Camerino – Århus Univ. – UC Madrid – Daresbury Laboratory

LBNL Berkeley –GANIL – JAEA

Work supported by BMBF (Nr. 06DA9036I), LOEWE / HIC for FAIR,

and the MINIBALL/REX-ISOLDE collaborations


Island of inversion
Island of inversion istopes on the

normal

sd

configurations

gs properties

Na

31Al

33Al

34Al

32Al

30Mg

33Mg

32Mg

31Mg

31Na

28Na

29Na

30Na

intruder

fp

configurations

MCSM, SDPF-M

Y. Utsuno et al.,

PRC 70, 044307 (2004)

November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 2


28 na level scheme
28 istopes on the Na – level scheme

  • No intruder component in gs wave

  • function (from g factor)

  • Excited states: correspondence

  • exp ó theory not obvious?!?

  • Low-lying negative parity states

  • predicted by MCSM

  • è Measure for size of the N=20 gap

Y. Utsuno et al., PRC 70, 044307 (2004)

V. Tripathi et al., PRL 94, 162501 (2005)

November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 3


Experimental programme

Possible future experiments: istopes on the

2H(28Na, 29Na)1H Q00 = 2.19 MeV

3H(27Na, 29Na)1H Q00 = -0.5 MeV

3H(28Na, 30Na)1H Q00 = -1.69 MeV

… to map transition into the „island“

Experimental programme

2H(27Na, 28Na)1H

Q00 = 1.32 MeV … optimal matching for population of states

in the region of interest

Competing reactions (PID needed):

(d,t) Q00 = -0.47 MeV

(p,d) Q00 = -4.07 MeV

28Na

27Na

29Na

30Na

November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 4


28 na 27 na n
| istopes on the 28Na> =|27Na> Ä |n>

27Na (5/2+): no intruder component in gs, odd proton in d5/2 orbital

Transfer to an odd-even nucleus … coupling of odd proton and odd neutron

Odd neutron in positive parity orbital d3/2

… positive parity states formed

Odd neutron in negative parity orbitals f7/2 or p3/2

… negative parity states formed

  • What happens to 27Na „core“ in 28Na??

  • èRelative spectroscopic factors

  • No intruder component in |27Na> core

  • è SFs large (e.g. for transfer to gs of 28Na)

  • Intruder component in |27Na> core

  • è SFs smaller

November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 5


2 h 27 na 28 na 1 h @ 3 mev u
2 istopes on the H(27Na,28Na)1H @ 3 MeV/u

  • FRESCO

  • optical potentials scaled from reactions with stable nuclei

  • all spectroscopic factors set to unity

DL=1,2,3

NEWS: MCSM can now calculate also SFs!!! (Y. Utsuno, priv. communication)

November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 6


Experimental set up 2008 t rex and miniball
Experimental set-up (2008) istopes on the - T-REX and MINIBALL

CD

beam

barrel

T-REX was funded and built by TU München,

KU Leuven, CSNSM Orsay, CERN, and

UK groups … (now also) TU Darmstadt

November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 7


2 h 27 na 28 na 1 h @ 3 mev u1
2 istopes on the H(27Na,28Na)1H @ 3 MeV/u

  • ds/dW: a few mb/sr J

  • pronounced angular distributions

  • èDL=1,2,3 well distinguishable J

„Blind“

zone

November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 8


T rex proposed improvement
T-REX … proposed improvement istopes on the

Detector arrangement now:

„blind“ zone around 90°

Target

New arrangements under consideration

or

… simulations needed to find optimum!

November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 9


Observables and results
Observables and results istopes on the

Data set rich of spectroscopic information

  • Angular distribution of protons

  • è orbital angular momentum transfer

  • è parity of states

  • Energies of protons and coincident g-rays

  • è level energies

  • Relative SFs

  • è identify possible intruder configuration (excitation of a neutron-pair

  • across N=20) in neutron wave function … at least qualitatively

  • Orbital angular momentum transfer

  • Relative SFs

  • Decay pattern of excited states

  • Angular distribution of g-rays

  • è … allows to determine (or, at least, to restrict) spin of states

November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 10


Beam intensity
Beam intensity istopes on the

  • standard UCx target, surface ionisation

ISAC-2 @ TRIUMF: 27Na, expected intensity 104/s

November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 11


Beam composition
Beam composition istopes on the

  • Contaminations: Al and small amount Mg (from Na decay)

  • … as seen in experiment IS482 (29,30Na)

  • Na/Al ratio much more favourable for lighter masses

  • because of larger Na and smaller Al yields

  • Monitored by DE-E telescope or Bragg chamber in beam dump

  • (d,p) reaction on 27Al: Q00 = 5.5 MeV

  • - stable nucleus (suppressed by time gate on proton impact)

  • - high-lying states populated

  • - level scheme and g-rays of 28Al well known (NNDC)

  • RILIS to improve Na/Al ratio???

  • - ionisation scheme exists and has been tested

  • U. Köster et al., Spec. Acta Part B 58, 1047 (2003)

  • - … high demand for RILIS

  • è NOT necessary for 27Na (maybe for 28Na in a future Addendum)

November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 12


Rate estimate and beam time request
Rate estimate and beam time request istopes on the

  • 2H(27Na, 28Na)1H @ 3 MeV/u … as first reaction of the programme

  • - First transfer experiment with an odd-even nucleus @ REX-ISOLDE

  • - Main physics aim: low-lying negative parity states è size of N=20 gap in 28Na

  • … explore the „shallow water around island of inversion“

  • Cross sections > 20 mb, target 5 mm CD2, eT-REX ≈ 62% and eMINIBALL ≈ 8%

  • è 400 protons/h (rate per populated state)

    è30 proton-g-coincidences/h

    (≈ 50 counts/peak in b-gated g-spectrum, V. Tripathi et al.)

  • è3000 counts (g-gated protons) in 4 days

    T-REX divided in 10 angular bins è >100 counts/bin, <10% statistical error

  • + 1 day for beam preparation

We request 15 shifts (5 days) of beam time

November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 13


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