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Gamma spectroscopy of n-rich 95,96 Rb nuclei

Gamma spectroscopy of n-rich 95,96 Rb nuclei by the incomplete fusion reaction of 94 Kr on 7 Li: Introduction to HIE-ISOLDE studies of n-rich Sb and Tl isotopes with Sn and Hg radioactive beam s Spokespersons: B. Fornal , S. Leoni Local contact: Magdalena Kowalska.

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Gamma spectroscopy of n-rich 95,96 Rb nuclei

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  1. Gamma spectroscopy of n-rich 95,96Rb nuclei by the incomplete fusion reaction of 94Kr on 7Li: Introduction to HIE-ISOLDE studies of n-rich Sb and Tl isotopes with Sn and Hg radioactive beams Spokespersons: B. Fornal, S. Leoni Local contact: Magdalena Kowalska B. Fornal1,B. Szpak1, P. Bednarczyk1, N. Cieplicka1, W. Królas1, A. Maj1, S. Leoni2,3, G. Benzoni3, N. Blasi3, S. Bottoni2,3, A. Bracco2,3, F. Camera2,3, F. Crespi2, B. Million3, A. Morales3, O. Wieland3, K. Rusek4, S. Lunardi5 , D. Mengoni5, F. Recchia5, C.A.Ur5, J. Valiente-Dobon6, G. de France7, E. Clement7, J. Elseviers8, F. Flavigny8, M. Huyse8, R. Raabe8, S. Sambi8, P. Van Duppen8, M. Sferrazza9 , G. Simpson10, G. Georgiev11, C. Sotty11 , A. Blazhev12, R. German12, B. Siebeck12, M. Seidlitz12, P. Reiter12, N. Warr12, S. Boenig13, S. Ilieva13, T. Kroell13, M. Scheck13, M. Thürauf13 ,R. Gernhaeuser14, D. Mücher14, R. Janssens 15, M.P. Carpenter15, S. Zhu15, N. M. Marginean16, D. Balabanski17, M. Kowalska18 1The Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Krakow, Poland; 2 Università degli Studi di Milano, Via Celoria 16, 20133, Italy; 3 INFN, sezione di Milano, Italy; 4 Heavy Ion Laboratory, University of Warsaw, Poland; 5 University of Padova and INFN sez. Padova, Italy; 6 Legnaro National Laboratory, Italy;7 GANIL, Caen, France; 8Instituut voor Kern-en Stralingsfysisca, K.U.Leuven, Belgium; 9Université libre de Bruxelles, Belgium; 10 LPSC Grenoble, France; 11CSNSM, Orsay, France; 12Institut fur Kernphysik der Universitat zu Koln, Germany; 13 TU Darmstadt, Germany; 14 TU Munchen, Germany 15 Argonne National Laboratory, USA; 16 IFIN-HH Bucharest, Romania; 17 IRNE-BAS, Bulgaria; 18ISOLDE, CERN, Switzerland

  2. Nature Effective Nuclear Force: 2-body, 3-body, … HOT topic in Nuclear Physics Z=82 Theory Shell Model Two body matrix elements from free NN potential Particle-Phonon Model coupling strength Experiment Near Magic Nuclei 132Sn and 208Pb 1 and 2 nucleons away 132Sb, 134Sb, 206Tl, 208Tl N=126 Z=50 • EXPERIMENTAL TOOLS • Fission, Fragmentation, transfer, deep-inelastic,… • YRAST Spectroscopy (limited information) N=82 Incomplete Fusion with 7Li:7Li(ASn,a2n), 7Li(AHg,a2n) High Spins, Excited States HIE-ISOLDE needed (4-5 MeV/u) to overcome Coulomb barrier

  3. Acquire Experience • with Incomplete Fusion Reactions with a RIB • - Reaction Mechanism, … • - Inverse kinematics, particle detection, … • - Backgrouds, … • Spectroscopy of 95,96Rb • - Moderate High Spins, Highly Excited States, … • - Region of Shape Changes from N=56 (spherical) to N=60 (deformed) • - r-process path, … TEST Case at REX-ISOLDE: Spectroscopy of n-rich 95,96Rb nuclei with 7Li(94Kr,axn) at ~ 3MeV/u maximum available energy

  4. Incomplete Fusion Reactions with 7Li: a spectroscopic tool 7Li → a+ t (binding energy Sa 2.5 MeV ) • From direct kinematics • 7Li + stable targets • Sizable cross Section of Incomplete Fusion • Favorable capture of t and emission of a • Evaporation of 2n and 1n • Population of n-rich systems • (not possible to reach by fusion) • Population of Off Yrast States • Intermediate Spins up to 12  • (in 124Sn(7Li,a2n)125Sb spins observed up to 23/2 ) IF fusion IF a2n a1n a G.D. Draculis et al., JPG23(1997)1191 D.S. Judson et al., PRC76(2007) 054306 R.M. Clark et al., PRC72(2005)054605 … M. Dasgupta et al., PRC66(2002), 041602R

  5. @ REX-ISOLDE: 7Li(94Kr,axn) Spectroscopy of 95,96Rb Shape changes with N number N. Marginean et al., PRC80(2009), 021301 subshell N=56 N=50 93-99Rb b-decay half-lives and neutron emission probabilities are different in DEFORMED and SPHERICAL nuclei Largeuncertainty in r-process location r-process S.Rahaman et al., Eur. Phys. J. A 32, 87 (2007) P. Delahaye et al., Phys. Rev. C74, 034331 (2006) P.Mӧller et al., Phys. Rev. C 67, 055802 (2003)

  6. Present Status on 95Rb Fission from 248Cm and 252Cf Coulex at MINIBALL G. Georgiev, C. Sotty, … et al. to be published G. Simpson et al., PRC82(2010) 024302 YRAST Spectroscopy 94Kr+7Li Intermediate spins (up to 15 )and Off Yrast States

  7. Our Incomplete Fusion REX-ISOLDE Proposal 94Kr (2.84 MeV/u) + 7LiF (1.5 mg/cm2) incomplete fusion DWBA Predictions for IF (by K. Rusek, Warsaw) Optical model potential from Julian Cook , NPA388(1982)153 aemission – Inverse Kinematics particleemission 232 MeV population of onlyone state at ~14.5 MeV  factor of 10-20 more expected  35-75 mb for 97Rb (and 95Rb) 7Li a EBeam 6Li t Mid-Target

  8. Experimental Setup: MINIBALL + T-REX Gamma spectroscopy tagging on a particles 19F 19F T-REX Simulation (R. Raabe) standard configuration DE-E Barrel: 140 + 1000 mm ( + 25mm mylar) DE-E CD: 500 + 1500 mm Input cross section: Elastic and DWBA 7Li 7Li a t a t a 19F t TRIGGER: (T-REX .AND. MB) 95,96Rb .OR. (g in MB)  97,98Y 7Li 80-90% Efficiency vs. theta lab

  9. Count Rates Estimate ELAB (94Kr) = 267 MeV IBEAM (94Kr) ≥ 2 x 105 pps 7LiF Target = 1.5 mg/cm2 s (axn) ≈ 50 mb Mg = 5 eMB7% eT-REX90 % events/s:  0.08 for a  0.03 for a-g 4 days (12 shifts):  104 eventsa-g Sufficient Statistics to perform basic g-spectroscopy studies of 95,96Rb • Question on Beam Purity: • 94Mo contaminanceNOT Critical (up to 50%): • - g-coincidences in MB will select nuclei of interest • Our Request: highest possible 94Kr current • High Instant current (94Kr+94Mb) can be accepted • Elastic scattering (7Li and 19F) reduced by mylar foil

  10. Thank you for the attention

  11. T-REX simulation (R. Raabe) • Input • cross sections: • Elastic (7Li and 19F) • DWBA “CLASSIC” Configuration: DE-E Barrel: 140 + 1000 mm (+25 mm mylar) DE-E CD: 500 + 1500 mm Beam Spot  = 3mm Target Position = (0,0) PADS 19F 19F 7Li 7Li 80-90% t a 232 MeV Efficiency vs. theta lab STRIPS 7Li 19F a a 7Li t a t 6Li t half barrel shown

  12. Importance of Nuclear Deformation for r-process b-decay half-lives and neutron emission probabilities are different in DEFORMED and SPHERICAL nuclei tb SPH ~ 7 x tbDEF PnSPH ~ 0.5 x PnDEF • Large uncertainty in • r-process location • difficoult to extrapolate • to more exotic regions P. Moller et al., Phys. Rev. C67, 055802 (2003) and ref. therein.

  13. Our Incomplete Fusion REX-ISOLDE Proposal 94Kr (2.84 MeV/u) + 7LiF (1.5 mg/cm2) DWBA Predictions (by K. Rusek, Warsaw) Optical model potential from Julian Cook , NPA388(1982)153 particleemission aemission – Inverse Kinematics 232 MeV population of only one state at ~14.5 MeV  factor of 10-20 more expected  35-75 mb for 97Rb (and 95Rb) 7Li a EBeam 6Li t Mid-Target

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