1. AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010 G. Duchêne Deformation in N=40 nuclei G. Duchêne, R. Lozeva, C. Beck, D. Curien, F. Didierjean, Ch. Finck, F. Nowacki, K. Sieja IPHC Strasbourg C. Domingo-Pardo, J. Gerl and the GSI group GSI Darmstadt D. Verney, F.Azaiez, S. Franchoo, F. Ibrahim, F. Le Blanc, I. Matea, M. Niikura, I. Stefan IPN Orsay

2. AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010 G. Duchêne Deformation in Fe and Cr nuclei E. Caurier et al., Eur. Phys. J A15 (2002) 145 Fe Cr

3. AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010 G. Duchêne 68 Ni Is 68 Ni a magic nucleus ?  Increase of the 2 1 + excitation energy  Reduction of the B(E2) value  No pronounced irregularity in the 2- neutron separation energy  Strong 2p-2h component -> excitation of a neutron pair into g 9/2 orbital  Major part of the B(E2) strength around 5 MeV Deformation in 68 Ni  68 Ni gs is spherical ( Gaudefroy et al., Phys. Rev. C80 (2009) 064313 )  Main 0 1 + state configuration is 4p-4h  Does not generate much deformation K. Langanke et al., Phys. Rev. C67 (2003) 044314

4. AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010 G. Duchêne In the vicinity of 68 Ni 67 Co  Collective 1p-2h proton intruder  First excited ½- state with large quadrupole deformation β ~ 0.25-0.4 D. Pauwels et al., Phys. Rev. C 78, 041307(R) (2009) 69 Cu  Measured magnetic moment of 13/2+ state  Considerable proton excitations across the Z=28 proton gap  Deviate from sphericity G. Georgiev et al., J. Phys. G: Nucl. Part. Phys. 28, 2993 (2002) 70 Zn  Given as a γ-soft nucleus ( Gaudefroy et al., Phys. Rev. C80 (2009) 064313 ) Hunt for deformation with np-nh configurations (n=6, 8) at higher excitation energy

5. AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010 G. Duchêne Shell-model calculations Valence space  40 20 Ca 20 core  π: f 7/2 + fp shell  υ: f 7/2 frozen + fp shell (p 3/2 frozen)+ g 9/2 + d 5/2  68 Ni: 8p-8h excitations  70 Zn: 6p-6h excitations  Huge matrices to diagonalise ~(500 10 6 )² to more than (10 9 )²  Several days calculation Results  68 Ni 8p-8h config: B(E2) down ~ 690 e²fm 4 Q 2 = -49 e.fm² β 2 ~ 0.32 E* ~ 13 MeV 6p-6h config: B(E2) down ~ 190 e²fm 4 Less deformation driving E* ~ 10 MeV  70 Zn 6p-6h config: B(E2) down ~ 695 e²fm 4 Q 2 = -48 e.fm² β 2 ~ 0.32 E* ~ 10 MeV All configurations are spread over many states when configuration mixing is allowed ! Mean field calculation in the β-γ plan

6. AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010 G. Duchêne Angular momentum and particle rates High-angular momentum states feeding  Several nucleon knock-out lead to « high-spin » transfers  8+ fed ~10 time less than 2+ state  Hypothesis: deformed structure feeding of 10% at 8 ħ Nuclei production rate  Primary beam: 76 Ge -> I max = 3 10 8 p/s  Primary Be/Nb target of 2.5 g/cm²  Al degrader of 1.5 g/cm²  Intermediate fragments: 73 Ga or 72 Zn  Rates calculations (slits cuts in S1, S3, S4) AGATA Lycca 10 5 Hz/wire 10 4 Hz Primary beam (p/s) Intermediate fragment Trans mission S4 rate (p/s) Reaction Final nucleus Production rate (p/s) 7 10 6 p/s 73 31 Ga30%10 4 fragmentation 68 28 Ni0.3 1p-2n knock- out 70 30 Zn18 3 10 7 p/s 72 30 Zn42%10 4 fragmentation 68 28 Ni2.5 2n knock-out 70 30 Zn35

7. AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010 G. Duchêne Gamma-ray statistics S’2 geometry  Full configuration: 10TC + 5DC -> 17%  Min. configuration: 5TC + 3DC -> 9% Intermediate fragment 72 Zn; 1.5 MeV gamma ray Experiment duration: 7 days Projectile Nucleus of interest AGATA config. γ - rate (min -1 ) Total counts singles in 7 days γ γ - rate (min -1 ) Total counts doubles in 7 days 72 Zn 68 Ni 2.5 p/s Full0.1919000.024244 Min0.1010000.006869 70 Zn 35 p/s Full2.66266000.343400 Min1.40140000.095950

8. AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010 G. Duchêne

9. AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010 G. Duchêne Ni-Zn-Ge Gaudefroy et al., Phys. Rev. C80 (2009) 064313 J. Van de Walle et al., Phys. Rev. Lett.99 (2007) 142501

10. AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010 G. Duchêne Tensor force Attractive between spin-flip orbitals  Attractive interaction πf5/2-νd5/2  Relaxed when removing protons from πf5/2 orbital  Excitation energy of νs1/2 state apparently decreases vs νd5/2 state π ν f 7/2 p 3/2 f 5/2 p 1/2 g 9/2 d 5/2 s 1/2 g 7/2 j+1/2 j-1/2