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Thorsten Kröll*

Thorsten Kröll*

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Thorsten Kröll*

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  1. 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

  2. Island of inversion 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

  3. 28Na – 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

  4. Possible future experiments: 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

  5. |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

  6. 2H(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

  7. Experimental set-up (2008) - 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

  8. 2H(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

  9. T-REX … proposed improvement 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

  10. Observables and results 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

  11. Beam intensity • 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

  12. Beam composition • 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

  13. Rate estimate and beam time request • 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