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Why are we (in general) interested in Q?

First combined DSAM and Coulex experiment at REX-ISOLDE – measuring the sign of the spectroscopic quadrupole moment of the 2 1 + state in neutron-rich 140 Ba *.

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Why are we (in general) interested in Q?

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  1. First combined DSAM and Coulex experiment at REX-ISOLDE – measuring the sign of the spectroscopic quadrupole moment of the 21+ state in neutron-rich 140Ba * Christopher Bauer1, Jörg Leske1, Thorsten Kröll1, Norbert Pietralla1, Vinzenz Bildstein2, Roman Gernhäuser2, Reiner Krücken2, Rudi Lutter3, Chavdar Stoyanov4, Dimitar Tarpanov4 1Institut für Kernphysik, TU Darmstadt, 64289 Darmstadt 2Physik-Department E12, TU München, 85748 Garching 3Maier-Leibnitz-Laboratorium, LMU München, 85748 Garching 4Institute for Nuclear Research and Nuclear Energy, 1784 Sofia, Bulgaria *supported by the BMBF (06 DA 9040 I) and HIC for FAIR 8.12.2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer

  2. Why are we (in general) interested in Q? • Q describes the deviation of the charge distribution from spherical symmetry in a nucleus • The intrinsic quadrupole moment Q0 (in the reference frame of the nucleus) is related to the deformation parameter β by • The observable is the spectroscopic quadrupole moment Q, which is related to Q0 in the case of the first 2+ state by 8.12.2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer

  3. The diagonal matrix element • The matrix elements are evaluated from measured yields / cross-sections in comparison with Coulomb excitation calculations M22 2+ 0+ M20 8.12.2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer

  4. The idea With new lifetime information the situation changes dramatically 8.12.2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer

  5. MINIBALL γ γ θγ θp 96Mo ExperimentMINIBALL at REX-ISOLDE (IS411) • Ebeam = 392 MeV • Target: 1mg/cm296Mo Barium (Z=56) 140Ba N=82 CD detector 132Sn RIB 140Ba Z=50 8.12.2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer

  6. DSAM analysis Additional run raw spectrum background subtracted • natCu target(thickness: 1mm) • 140Ba is stopped 602 keV 602 keV Time difference [µs] Energy [keV] 8.12.2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer

  7. DSAM analysis: Fit • 20 individual fits for each MB Ge core in this experiment • weighted average t = 12.5(6) ps The DSAM fit was done by J. Leske. 8.12.2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer

  8. Coulex cross-section The cross-section is sensitive on the quadrupole moment! Sensitivity S = (sQ+-sQ-)/sQ0 8.12.2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer

  9. Complete statistics The new determined lifetime fixes the M20 matrix element. Old lifetime: 14(6) ps New Lifetime: 12.5(6) ps 8.12.2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer

  10. Splitted statistics The quadrupole moment must be positive! -> OBLATE SHAPE Comparison to theory QPM: Q = 0.1 (M22 = 0.13) 8.12.2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer

  11. γ I γ J F I Recoil-in-vacuum natCu (892mg/cm2) Ion beam (140,142Ba) 96Mo (0.9mg/cm2) Ion beam (140,142Ba) e- 15.4.2010 | MINIBALL Workshop Leuven | IKP Darmstadt | Christopher Bauer

  12. Angular Distributions • Thick target: natCu • 142Ba, distribution for 360 keV line ( ) 15.4.2010 | MINIBALL Workshop Leuven | IKP Darmstadt | Christopher Bauer

  13. g factor • Limit for g ( ) in 140Ba is |g|≤0.38 • RIV method is applicable • But need appropriate calibration isotope(s) 8.12.2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer

  14. Summary Results Conclusions Both methods are complementary to standard MINIBALL experiments Need extra run with suitable thicker target for DSAM Need extra runs for distribution without deorientation and with calibration isotope(s) g factor Be aware of contamination! • 140Ba Coulex evaluation • Lifetime:t = 14(6) ps 12.5(6) ps21(9) W.u. 18.8(9) W.u. • Qspec > 0 oblate shape • RIV method • First time tested at REX-ISOLDE • Limit for g( )-factor in 140Ba|g|≤0.38 Thank you for your attention! 15.4.2010 | MINIBALL Workshop Leuven | IKP Darmstadt | Christopher Bauer

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