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* Work supported by BMBF (Nr. 06DA9036I), LOEWE / HIC for FAIR, and the MINIBALL/REX-ISOLDE collaborations *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 CERN-INTC-2009-037, INTC-P-272

2. November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 2 Island of inversion normal sd configurations 30 Mg 29 Na 33 Al 32 Al 31 Al 31 Mg 32 Mg 30 Na 31 Na 34 Al 33 Mg intruder fp configurations Na 28 Na MCSM, SDPF-M Y. Utsuno et al., PRC 70, 044307 (2004) gs properties

3. November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 3 28 Na – level scheme V. Tripathi et al., PRL 94, 162501 (2005) No intruder component in gs wave function (from g factor) Excited states: correspondence exp  theory not obvious?!? Low-lying negative parity states predicted by MCSM  Measure for size of the N=20 gap Y. Utsuno et al., PRC 70, 044307 (2004)

4. November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 4 Experimental programme Q 00 = 1.32 MeV … optimal matching for population of states in the region of interest Competing reactions (PID needed): (d,t) Q 00 = -0.47 MeV (p,d) Q 00 = -4.07 MeV 29 Na 30 Na 28 Na 27 Na Possible future experiments: 2 H( 28 Na, 29 Na) 1 H Q 00 = 2.19 MeV 3 H( 27 Na, 29 Na) 1 H Q 00 = -0.5 MeV 3 H( 28 Na, 30 Na) 1 H Q 00 = -1.69 MeV … to map transition into the „island“ 2 H( 27 Na, 28 Na) 1 H

5. November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 5 27 Na (5/2 + ): no intruder component in gs, odd proton in d 5/2 orbital Transfer to an odd-even nucleus … coupling of odd proton and odd neutron Odd neutron in positive parity orbital d 3/2 … positive parity states formed Odd neutron in negative parity orbitals f 7/2 or p 3/2 … negative parity states formed  28 Na> =  27 Na>  n> What happens to 27 Na „core“ in 28 Na??  Relative spectroscopic factors No intruder component in | 27 Na> core  SFs large (e.g. for transfer to gs of 28 Na) Intruder component in | 27 Na> core  SFs smaller

6. November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 6 2 H( 27 Na, 28 Na) 1 H @ 3 MeV/u  L=1,2,3 FRESCO optical potentials scaled from reactions with stable nuclei all spectroscopic factors set to unity NEWS: MCSM can now calculate also SFs!!! (Y. Utsuno, priv. communication)

7. November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 7 Experimental set-up (2008) - T-REX and MINIBALL beam barrel CD T-REX was funded and built by TU München, KU Leuven, CSNSM Orsay, CERN, and UK groups … (now also) TU Darmstadt

8. November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 8 2 H( 27 Na, 28 Na) 1 H @ 3 MeV/u d  /d  : a few mb/sr pronounced angular distributions   L=1,2,3 well distinguishable „Blind“ zone

9. November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 9 T-REX … proposed improvement Detector arrangement now: „blind“ zone around 90° New arrangements under consideration Target … simulations needed to find optimum! or

10. November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 10 Observables and results Angular distribution of protons  orbital angular momentum transfer  parity of states Energies of protons and coincident  -rays  level energies Relative SFs  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  -rays  … allows to determine (or, at least, to restrict) spin of states Data set rich of spectroscopic information

11. November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 11 Beam intensity T 1/2 [ms] PSB Yield [/  C] Intensity IS482 [/s] Estimate [/s] 27 Na3018.5·10 6 2·10 5 28 Na30.59.6·10 5 < 2·10 4 29 Na44.91.5·10 5 3-4·10 3 30 Na485.1·10 4 0.6-1·10 3 ISAC-2 @ TRIUMF: 27 Na, expected intensity 10 4 /s standard UC x target, surface ionisation

12. November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 12 Beam composition Contaminations: Al and small amount Mg (from Na decay) … as seen in experiment IS482 ( 29,30 Na) Na/Al ratio much more favourable for lighter masses because of larger Na and smaller Al yields Monitored by  E-E telescope or Bragg chamber in beam dump (d,p) reaction on 27 Al: Q 00 = 5.5 MeV - stable nucleus (suppressed by time gate on proton impact) - high-lying states populated - level scheme and  -rays of 28 Al 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  NOT necessary for 27 Na (maybe for 28 Na in a future Addendum)

13. November 16, 2009 | INTC Meeting | TUD - Institut für Kernphysik | Thorsten Kröll | 13 Rate estimate and beam time request 2 H( 27 Na, 28 Na) 1 H @ 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  size of N=20 gap in 28 Na … explore the „shallow water around island of inversion“ Cross sections > 20 mb, target 5  m CD 2,  T-REX ≈ 62% and  MINIBALL ≈ 8%  400 protons/h (rate per populated state)  30 proton-  -coincidences/h (≈ 50 counts/peak in  -gated  -spectrum, V. Tripathi et al.)  3000 counts (  -gated protons) in 4 days T-REX divided in 10 angular bins  >100 counts/bin, <10% statistical error + 1 day for beam preparation We request 15 shifts (5 days) of beam time