Stephane Grévy : June 2, 2014 Properties of intruder states in 34 Al 21 and 34 Si 20 IFIN - Bucharest GANIL - Caen CENBG - BordeauxIPN - Orsay Atomki - DebrecenFLNR - Dubna NPI - RezIPHC - Strasbourg University of Madrid CEA - Bruyères-le- Châtel ISOLDE - GenevaINFN - Padova 1- intruder state in 34 Si GANIL - E594 : beta decay of 34 Al F. Rotaru et al., PRL109(2012) 2- intruder 1 + state in 34 Al ?ISOLDE - IS530 : beta decay of 34 Mg R. Lica et al., under analysis

 state in 34 Si : how the intruder configurations develop at N=20 2ħ  32 Mg 0ħ  Nħ  ? 34 Si 0ħ  Nħ  S 32 Mg 36 S 34 Si 30 Mg 28 Mg Follow the evolution of the intruder configurations from the stability towards the Island of Inversion  Study the evolution of the excited 0 + states 0ħ  2ħ  0ħ  Nħ  28 Mg 30 Mg O + 2 ( 30 Mg) : W. Schwerdtfeger, PRL ħ  O + 2 ( 32 Mg) : K. Wimmer, PRL The "island of inversion" around 32 Mg + central part tensor part

34 Al N=20 40 Ca 38 Ar 36 S 30 Ne 32 Mg 34 Si Search for the state in 34 Si  hypothesis : the could be directly populated through the  -decay of a predicted isomeric 1 + state in 34 Al. -All experiments failed in this quest…  inelastic scattering,  -decay of 34 Al,… 34 Al : 4 - ground state   d 5/2 ) 5   d 3/2 ) +4 (f7/2) Si : deformed state   (d 5/2 ) 6   d 3/2 ) -2 (f7/2) Si : 0 + ground state   (d 5/2 ) 6   d 3/2 ) Al : 1 + excited state (E~200 keV)   d 5/2 ) 5   d 3/2 ) -1 (f7/2) +2 Almost all the calculations predict the state to be located below the  decay by : - internal pair creation - internal conversion electron [if E (0 + 2 ) <1022 keV - not expected] 2ħ 

b Experiment : - production the 34 Al in the "predicted" isomeric 1 +  projectile GANIL/LISE - implantation in a Kp foil E1D6 E2XY Edeg1&2 Erot1 GANIL/LISE3 Experiment, may 2010 e+ e in 34 Si : the experiment F. Rotaru et al., Phys. Rev. Lett.109 (2012)  - measurement of the gamma-rays  2 Ge clovers (EXOGAM) - trigger on the  -decay from the gs and the isomer and measurement of the energy of both e + and e - in coincidence  4 Si-SiLi telescopes

44 44 E e1 +E e2 = cst = 1697(3) keV E(0 + 2 ) = 1697 keV in 34 Si : experimental results 1/3 2719(3) e + e - -- T 1/2 (0 + 2 ) = 19.4(7) ns Electric monopole strength: ρ 2 (E0)=(13 ± 0.9)x (7) ns = 2719(3) F. Rotaru et al., Phys. Rev. Lett.109 (2012)092503

2719(3) 4 in 34 Si : experimental results 2/3 26 (1) msec Beta decay time from 34 Al : e + e (7) ns 54.4 (5) msec -- 26 (1) msec F. Rotaru et al., Phys. Rev. Lett.109 (2012)092503

2719(3) 4 (1) msec in 34 Si : experimental results 3/3 B(E2:2 + 1  ) from - B(E2:2 + 1  ) = 17(7) e 2 fm 4 Coulex : Ibbotson, PRC80(1998) I  (3326 keV)/I  (606 keV) = 1380(717) B(E2:2 + 1  ) = 61(40) e 2 fm 4 ? 17(7) F. Rotaru et al., Phys. Rev. Lett.109 (2012) (7) ns

2719(3) 4 (1) msec in 34 Si : mixing and deformation  mixing of the 0 + states : cos²  ~ 0.22 B(E2:  ) = 17(7) e²fm 4 +  ² = (3Z/4p)²cos²  cos²  1 ²-  2 ²)² if spherical-deformed configuration   2 = 0   2 ~ 0.29 B(E2:  ) = 61(40) e²fm 4  ²(E0:  ) = 13.0(0.9) mu 17(7) 61(40) F. Rotaru et al., Phys. Rev. Lett.109 (2012) (7) ns

d 3/2 s 1/2 d 5/2 f 7/2 7/2 - 3/2+ d 3/2 s 1/2 d 5/2 f 7/2 7/2 - 3/2 + d 3/2 s 1/2 d 5/2 f 7/2 2ħ  in 34 Si : np-nh excitations From Heyde and Wood, Rev. Mod. Phys.  The energy of the in 34 Si is in agreement with a 2p-2h character

In particular, the major pillars to understand the Island of Inversion are the 0 + 1,2 states in 30 Mg, 32 Mg and 34 Si Important to have a interaction capable of describing various situations in a unified manner. gs 0 + sph 0 + def 34 Si 32 Mg MeV - removal of two protons from 34 Si  4 MeV shift gs 0 + sph 0 + def 30 Mg 32 Mg MeV - addition of two neutrons to 30 Mg  3 MeV shift A good interaction should therefore be able to reproduce : in 34 Si : Shell model calculations

SDPF-U-SI interaction : F. Nowacki and A.Poves, PRC79(2009) valence protons :sd shell - valence neutrons :sd or pf shell  no (sd  pf) neutron excitations  labeled "0ħ  " 8 8  8 20  not able to describe nuclei in wich neutron excitations from sd to pf are important such as, by definition, in the "island of inversion" To account for (sd  pf) neutron excitations : A. Poves & Strasbourg/Madrid coll. 8 8 off diagonal matrix elements - Lee-Kahana-Scott G matrix - scaled as for the description of the SD states in 40 Ca (multi p-multi h excitations) neutron SPE's for sd-pf shells on a 16 O core - sd  standard USD - fp  no experimental guidance  SDPF-U-SI in case of 0ħ  limit  ( 30 Mg) at the correct energy  SDPF-U-MIX interaction decrease of the 0 + def 34 Si  32 Mg 30 Mg  32 Mg Expt. SM

Intruder 1+ state in 34 Al : ISOLDE Experiment IS530  34 Mg beta decay experiment at ISOLDE 34 Al : 4 - ground state   d 5/2 ) 5   d 3/2 ) +4 (f7/2) Al : 1 + excited state   d 5/2 ) 5   d 3/2 ) -1 (f7/2) Al 4-4- (1 + ) ? 26(1)ms 54.4(5)ms 34 Mg 0+0+

Motivations :  Measure the excitation energy of the newly observed 1 + isomer;  First time measurement of the gamma rays following the β- decay of 34 Mg  Build the first level scheme for 34 Al  Measure the intensity of the (2 + → ) transition in 34 Si  B(E2 :  2+) Intruder 1+ state in 34 Al : ISOLDE Experiment IS530

Structure – based on OSIRIS (Bucharest) 3 CLOVER detectors (Bucharest) 1 HPGe detector (90%) (Strasbourg) 5 LaBr 3 detectors (4 Legnaro, 1 Bucharest) ~4  NE102 plastic scintilator (Bucharest) 3 neutron detectors (NE213 DEMON, Strasbourg) Tape station (Strasbourg) Data ACQ (Bucharest) Intruder 1+ state in 34 Al : ISOLDE Experiment IS530 september 2012

Scarce information for 34 Al in ENSDF (Coul.Ex.) Many strong unassigned gammas observed in the beta gated HPGe spectra F.Rotaru et al., PRL 109, (2012) ENSDF Intruder 1+ state in 34 Al : ISOLDE Experiment IS530 IS530 data

34 Si I β (%) e-e- e+e  First time measurement of the gamma rays following the β- decay of 34 Mg  The first level scheme for 34 Al  New half-life for 34 Mg – 63(1)ms  Improved level scheme for 34 Si  100% feeding of the 1 + in 34 Mg  34 Al  no information about the excitation energy of the 1 + state Intruder 1+ state in 34 Al : ISOLDE Experiment IS530

 Crossing between 33 Mg and 34 Al !  unexpeted… (attractive p-n int.)  4 - is believed to be the g.s. because it was observed first using an ISOL technique  slow  4 - (54ms) could be favored / 1 + (26ms)  it could be the isomer !  mass measurement of the 1 + state after  -decay of 34 Mg proposal at ISOLTRAP and TITAN Intruder 1+ state in 34 Al : isomer or ground state ? A. Chaudhuri et al., Phys. Rev. C88(2013) november 2013

Perspectives (from an experimental point of view) Better characterize the isomer/ground state in 34 Al  g factor measurement (accepted experiment at GANIL)  mass measurement (accepted at ISOLDE and TRIUMF) Conclusions state in 34 Si  better characterization of the shape coexistence at N=20 extention of the the SDFP-U-SI interaction  neutron excitation above N=20  SDPF-U-MIX : description of both the N=20 and N=28 regions first study of the beta-decay of 34 Mg  new T 1/2  first level scheme in 34 Al (above 1+ state)

R.Lică 1, F.Negoiă 1, S.Grevy 2, N.Mărginean 1, Ph.Desagne 3, T.Stora 4, F.Rotaru 1, C.Borcea 1, R.Borcea 1, S.Călinescu 1, J.M.Daugas 5, D.Filipescu 1, I.Kuti 8, L.Fraille 9, S.Franchoo 6, I.Gheorghe 1, D.G.Ghiţă 1, R.Mărginean 1, C.Mihai 1, P.Mourface 6, P.Morel 5, J.Mrazek 7, A.Negre 1, D.Pietreanu 1, T.Sava 1, D.Sohler 8, M.Stănoiu 1, I.Stefan 6, R.uvăilă 1, S.Toma 1, C.A.Ur 1,10 1 IFIN-HH, Bucharest, Romania, 2 CENBG, Bordeaux, France 3 IPHC, Strasbourg, France 4 ISOLDE/CERN, Geneva, Switzerland 5 CEA, DAM, DIF Arpajon, France 6 IPN, Orsay, France 7 NPI, AS CR, Rez, Czech Republic 8 Atomki, Debrecen, Hungary 9 Universidad Complutense, CEI Moncloa, Madrid, Spain 10 INFN - Sezione di Padova, Italy

backup slides

0 + 2 in 34 Si : Shell Model calculations  Excellent agreement experiment – Shell Model SDPF-U-MIX b (3) b b 61(40) 17(7) % 2p-1h % 0ħ  % 2p-2h ~ % 30% 60% 30 ms 59 ms 26(1)ms 54.4(5)ms % 0ħ  decrease of the 0 + def 34 Si  32 Mg 30 Mg  32 Mg Expt. SM