1. NUPECC – Bucharest – Oct. 2007 NUCLEAR SPECTROSCOPY AT THE DEPARTMENT OF NUCLEAR PHYSICS – TANDEM BUCHAREST

2. NUPECC – Bucharest – Oct. 2007 1974 – 7 MV 2007 – 9 MV 3 ion sources: - duoplasmatron (HVEC) - sputtering (NEC) - AMS ultraclean (sputtering) beams: p to Au (no noble gases) (~ 3600 hours/year) foil and gas stripping 7 beamlines Since 2006 Refurbishing process: - Vacuum equipment √ - Electrical power supplies √ - Voltage charging system (Pelletron) √ - Sputtering ion source √ - Automatic control of ion optics & diagnosis - Beam pulsing system

3. NUPECC – Bucharest – Oct. 2007 Experimental Nuclear Spectroscopy program at the Bucharest Tandem accelerator Medium / high-spin γ-ray spectroscopy with heavy-ion fusion-evaporation reactions ( check of structure models: shell model, IB(F)M ) Low-spin γ-ray spectroscopy with p/α beams (quasicomplete level schemes, DSAM lifetimes) Beta decay studies ( tests of critical point symmetries ) Reactions of astrophysical interest [ (α,γ) ]

4. NUPECC – Bucharest – Oct. 2007 Heavy-ion fusion-evaporation reactions

5. NUPECC – Bucharest – Oct. 2007 139 Ce Low spins – quasicomplete low-spin scheme 139 La(p,nγ) reaction, E p = 5-6 MeV High spins – 130 Te( 12 C,3nγ), 50 MeV D.Bucurescu et al, Eur. Phys. J. A27 (2006) 301

6. NUPECC – Bucharest – Oct. 2007 E(5): critical point of transition U(5) (sph. vibr.) to O(6)(γ -soft) (2.00, -1.0) (2.50,-2.0) C.Mihai et al, Phys. Rev. C75(2007)044302 12 C: 36 MeV, 3 pnA, t=250 s, 54 Fe: 13mg/cm 2, 99% 3HPGe detectors ~30% eff. E(5) Candidates

7. NUPECC – Bucharest – Oct. 2007 64 Zn 66 Zn 68 Zn 10540.53 - <0.66210(75)>430 E(5) 0.12 32

8. NUPECC – Bucharest – Oct. 2007

9. Multi-purpose gamma-miniarray 3 new HPGe (pop-top) (eff.: 2 x 60%; 1 x 30%) + 3 older ~30% + clover (to come) + … Under installation: 2007-2008: 6 Osiris detectors with anticompton shields Under execution: Plunger device (“Kőln”)

10. NUPECC – Bucharest – Oct. 2007 European Collaborations Collaborations with different Labs and Universities (bilateral and governmental collaboration agreements) EURONS ( AGATA, EXOCHAP, ISIBHI, EWON ) EURISOL ( fission target; safety&radioprotection; physics&instrumentation ) FAIR (NUSTAR) Padova – Legnaro ; GANIL

11. NUPECC – Bucharest – Oct. 2007 Collaboration with Lab. Naz. Legnaro 1)The heaviest even-even N=Z and odd-A N=Z+1 nuclei ( A > 80, 100 Sn) Fusion-evaporation reactions. GASP (γ); ISIS (charged particles); N-ring (n)

12. NUPECC – Bucharest – Oct. 2007

13. T=0 np pairing in N=Z nuclei (?) Evolution of collectivity ( along N=Z line ) Critical point symmetry (X(5) at N ≈ Z ≈ 38,40 ? ) Spin-gap isomers ( close to N=Z=50 ) Shell model description ( test current resid. inter. ) T=0 np pairing in N=Z nuclei (?)

14. NUPECC – Bucharest – Oct. 2007 J=0 T=1 J=1…2j T=0 Signature of T=0 np pairing ? Delayed Alignment in N=Z Nuclei N.Marginean et al, Phys. Rev. C63 (2001) 031303(R); C65(2002)051303(R)

15. NUPECC – Bucharest – Oct. 2007 2)Spectroscopy of neutron-rich nuclei Multi-fragmentation reactions. CLARA (γ); PRISMA (product nuclei) 58 Cr: yrast line – E(5) symmetry vs shell model Neutron-rich Fe nuclei (A = 61 to 66) – test of “fpg” residual interaction in large-scale SM calculations Spherical n-rich 89 Rb, 92,93 Y – test of “gwbxg” residual interaction

16. NUPECC – Bucharest – Oct. 2007 D.Bucurescu et al, Phys. Rev. C, in press 89 Rb

17. NUPECC – Bucharest – Oct. 2007 3) High-spin states of light nuclei (sd shell) Tests of large scale shell model calculations (sdfp residual interaction) Isospin symmetry > Large MED between ~pure sp (f 7/2 ) analog states; > Different E1 decay pattern of analog pos. parity states:  importance of multipole Coulomb & electromagnetic spin-orbit terms. F. Della Vedova et al, Eur. Phys. J. A27 (2006) 301

18. NUPECC – Bucharest – Oct. 2007 3) Nuclear moment measurements – ns-μs isomers - g-factors - TDPAD method, H ext ; - electric quadrupole moments (Q) – Electric Field Gradients - electric quadrupole moments (Q s ) – Electric Field Gradients (noncubic crystalline lattices) (noncubic crystalline lattices) High K isomers: I π =14 + in 176 W : well defined K=14, deformed pure 4-qp state; anomalous decay due to K mixing in lower K states. Q s for normal and intruder states in 192,194 Pb (11 -, 12 + ): shape mixing Q s for magnetic rotational bandhead in 193 Pb

19. NUPECC – Bucharest – Oct. 2007 Q s 29/2 - magnetic rotational bandhead in 193 Pb | Q s | (exp) Q s (PQTAC) β 2 29/2  (1i 13/2  1 )   ( 1i 13/2 1h 9/2 ) 2.84 (26) eb –2.8 eb – 0.12 21/2  (1i 13/2  2 )  3p 1/2 0.22(2) eb +0.26 eb +0.02 33/2  (1i 13/2  3 ) 0.45(4) eb +0.46 eb +0.03 EFG Hg crystalline lattice T=170 K M. Ionescu-Bujor et al., Phys. Rev. C 70, 034305 (2004) and to be published 21/2 - E  =184 keV 29/2 - E  =213 keV T 1/2 = 9 ns T 1/2 = 22 ns T 1/2 = 180 ns 33/2 + E  =532 keV

20. NUPECC – Bucharest – Oct. 2007 On proton-rich side:  Discovery of Doubly Magic 48 Ni  Two-Proton Radioactivity of 45 Fe  First Observation of 55, 56 Zn  First observation of 54 Zn and its decay by two-proton emission On neutron-rich side:  Evidence for 34 Ne, 37 Na in a search for 40 Mg (not observed) deduced particle instability of 33 Ne, 36 Na Contributions to Nuclear Structures Studies at GANIL  Search for new nuclei and new decay modes

21. NUPECC – Bucharest – Oct. 2007  Focal plane γ-spectroscopy: β-decay and new isomers  β-delayed γ-n spectroscopy (with TONNERRE coupled to clover detectors) of very neutron rich nuclei around N=20 and N=28:  β-decay of 32,33 Mg and level scheme of 32,33 Al.  limits of the island of inversion located around N=20 are not well defined.  neutron-rich nuclei around N=28: new lifetimes for 12 nuclei, new P n probabilities, new transitions in 45,46 Ar.  New Island of μs Isomers in Neutron-Rich Nuclei Around Z = 28 and N = 40: study of 71 Co, 73 Co, 76 Ni, 67 Fe, 72 Ni  New Shape Isomer in the Self-Conjugate Nucleus 72 Kr (0 + isomer measured with combined γ – CE spectroscopy)  Observation of 0 + isomer in 44 S (shape coexistence) TONNERRE multidetector, built jointly by IFIN-HH and LPC-Caen; used in GANIL and ISOLDE/CERN  Observation of 0 + isomer in 44 S (shape coexistence)

22. NUPECC – Bucharest – Oct. 2007 Combined CE-  spectroscopy of isomers populated in fragmentation 0 + isomer observed in 44 S, and known isomer in 43 S -- interpreted as shape coexistence evidence in neutron rich N=28 nuclei 44 S  =2.3±0.3 μs Grevy et al., EPJA (ENAM 04) Sarazin et al., PRL 84(2000)5062 Nummela et al., PRC 63(2001)044316

23. NUPECC – Bucharest – Oct. 2007 Fragmentation reactions (double fragmentation) to populate excited states in extremely far from stability nuclei. ( SPEG spectrometer and Chateau de Cristal)  Search for neutron excitations across the N = 20 shell gap in 25-29 Ne  N = 14 and 16 shell gaps in neutron-rich oxygen isotopes  Structure of the neutron-rich 37, 39 P and 43, 45 Cl nuclei  Shape evolution in heavy sulfur isotopes and erosion of the N=28 shell closure  Recent experiment for 42 Si and 36 Ca ( collapse of N=28 magicity )  In-beam γ– ray spectroscopy  Recent experiment for 42 Si and 36 Ca ( collapse of N=28 magicity )

24. NUPECC – Bucharest – Oct. 2007 E (2+) MeV Collapse of N=28 Shell Closure in 42 Si B. Bastin et al., PRL99(2007)022503 40 Si 42 Si EE M/Q Identification after 2 nd fragmentation using SPEG spectrometer Chateau de Cristal  -detector 44 S secondary beam New experimental results and shell model calculations indicate that 42 Si is best described by a well deformed oblate rotor

25. NUPECC – Bucharest – Oct. 2007 Research group: senior researchers: 8 researchers: 5 PhD students: 6

26. NUPECC – Bucharest – Oct. 2007

32. 188 Pb triple shape coexistence 12  spherical 11 – oblate 8 – prolate (1i 13/2 ) 2  (1i 13/2 1h 9/2 ) (1i 13/2 1h 9/2  1 ) G.D.Dracoulis et al., Phys.Rev. C 67, 051301(R) (2003) Static moment experiments - in progress at LNL

33. NUPECC – Bucharest – Oct. 2007  New Island of μs Isomers in Neutron-Rich Nuclei Around the Z = 28 and N = 40 Shell Closures  Beta-decay of 71 Co and 73 Co  Evidence for an isomer in 76 Ni  Isomeric decay of 67 Fe -- Evidence for deformation  Low energy levels in 72 Ni  New Shape Isomer in the Self-Conjugate Nucleus 72 Kr (0 + isomer measured with combined – CE spectroscopy)  Observation of 0 + isomer in 44 S (shape coexistence)  Focal plane γ– spectroscopy. β-decay and New Isomers  Observation of 0 + isomer in 44 S (shape coexistence)

34. NUPECC – Bucharest – Oct. 2007  -delayed n-  spectroscopy with TONNERRE TONNERRE installed in focal plane of LISE-III Spectrometer TONNERRE was built joint by IFIN-HH and LPC-Caen. It has ~ 50% angular coverage and 25% typical intrinsic resolution for few MeV neutrons. The threshold corresponds to about 300 keV neutron energy. TONNERRE was used in GANIL and ISOLDE/CERN. 32 Mg decay Typical implantation setup allows measurements of  -  -n coincidences.

35. NUPECC – Bucharest – Oct. 2007 F. Della Vedova et al, Eur. Phys. J. A27 (2006) 301 > Large MED between ~pure sp (f 7/2 ) analog states; > Different E1 decay pattern of analog pos. parity states:  importance of multipole Coulomb & electromagnetic spin-orbit terms.

36. NUPECC – Bucharest – Oct. 2007 4) Nuclear moment measurements  isomers ns - µs Home new isomers, g, Q s → Home new isomers, g, Q s → nuclei near stability INFN g, Q s → INFN LNL g, Q s → neutron deficient nuclei A  180 K isomers, shape coexistence in Pb GSI RISING collaboration g → GSI RISING collaboration g → neutron rich nuclei Dedicated experiments Hyperfine interactions  TDPAD method EFG Dedicated experiments Hyperfine interactions  TDPAD method g factors H ext Q s V zz Electric Field Gradients noncubic crystalline lattices

37. NUPECC – Bucharest – Oct. 2007 LNL 164 Dy( 16 O,4n) 176 W LNL 164 Dy( 16 O,4n) 176 W 83 MeV Pulsed beam  T=2 ns T rep =800 ns g Q s 176 W I  = 14 + high K isomer B. Crowell et al., PRL 72, 1164 (1994) High K states E transitions = ΔK – degree of K forbiddenness f = (T 1/2  /T 1/2 W ) 1/ Anomalous decay f 917 keV 2.3 714 keV 3.0 945 keV 3.6 f ν  100 normal decay T 1/2 =41(1) ns

38. NUPECC – Bucharest – Oct. 2007 M. Ionescu-Bujor et al., Phys. Lett. B 495, 289 (2000) Phys. Lett. B 541, 219 (2002) g factor H ext = 27.5 kG Q s EFG Tl crystalline lattice g exp = + 0.462 (11) | Q s | = 6.0 (7) eb  7/2 + [404] 9/2 - [514] 5/2 - [512] 7/2 + [633]  2 (14 + ) = 0.29(4) deformed pure four – quasiparticle configuration well defined K = 14 anomalous decay due to K mixing in the lower K states 176 W I  =14 +

39. NUPECC – Bucharest – Oct. 2007 11 - → 2.9 (3) eb 3.6(4) eb 12 + → 0.32 (4) eb 0.48 (3) eb M. Ionescu-Bujor et al., Phys. Lett. B 650, 141 (2007) T 1/2 = 758 nsT 1/2 = 133 ns T 1/2 = 370 ns T 1/2 = 1080 ns Q s normal and intruder states in 192,194 Pb 12  (1i 13/2 ) 2 11   1i 13/2 1h 9/2 12 + ---- PQ ---- PQ TAC  2  + 0.02  2  –0.12 11  IBM HFB Q o (11 , 192 Pb)  shape mixing EFG Bi crystalline lattice