First combined DSAM and Coulex experiment at REXISOLDE
First combined DSAM and Coulex experiment at REX-ISOLDE – measuring the sign of the spectroscopic quadrupole moment of the 21+ state in neutron-rich 140 Ba * Christopher Bauer 1, Jörg Leske 1, Thorsten Kröll 1, Norbert Pietralla 1, Vinzenz Bildstein 2, Roman Gernhäuser 2, Reiner Krücken 2, Rudi Lutter 3, Chavdar Stoyanov 4, Dimitar Tarpanov 4 1 Institut fu r Kernphysik, TU Darmstadt, 64289 Darmstadt E 12, TU Mu nchen, 85748 Garching 3 Maier-Leibnitz-Laboratorium, LMU Mu nchen, 85748 Garching 4 Institute for Nuclear Research and Nuclear Energy, 1784 Sofia, Bulgaria 2 Physik-Department *supported by the BMBF (06 DA 9040 I) and HIC for FAIR 8. 12. 2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer
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 Q 0 (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 Q 0 in the case of the first 2+ state by 8. 12. 2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer
The diagonal matrix element M 22 2+ M 20 0+ The matrix elements are evaluated from measured yields / cross -sections in comparison with Coulomb excitation calculations 8. 12. 2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer
The idea With new lifetime information the situation changes dramatically 8. 12. 2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer
Experiment MINIBALL at REX-ISOLDE (IS 411) N=82 Barium (Z=56) 140 Ba Ebeam = 392 Me. V Target: 1 mg/cm 2 96 Mo MINIBALL 132 Sn Z=50 γ γ θγ θp 96 Mo RIB 140 Ba 8. 12. 2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer CD detector
DSAM analysis Additional run nat. Cu target (thickness: 1 mm) 140 Ba is stopped raw spectrum 602 ke. V background subtracted Time difference [µs] 602 ke. V Energy [ke. V] 8. 12. 2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer
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
Coulex cross-section The cross-section is sensitive on the quadrupole moment! Sensitivity S = (s. Q+-s. Q-)/s. Q 0 8. 12. 2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer
Complete statistics The new determined lifetime fixes the M 20 matrix element. Old lifetime: 14(6) ps New Lifetime: 12. 5(6) ps 8. 12. 2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer
Splitted statistics The quadrupole moment must be positive! -> OBLATE SHAPE Comparison to theory QPM: 8. 12. 2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer Q = 0. 1 (M 22 = 0. 13)
Recoil-in-vacuum γ Ion beam (140, 142 Ba) I nat. Cu (892 mg/cm 2) γ Ion beam (140, 142 Ba) 96 Mo J e- I F (0. 9 mg/cm 2) 15. 4. 2010 | MINIBALL Workshop Leuven | IKP Darmstadt | Christopher Bauer
Angular Distributions Thick target: nat. Cu 142 Ba, distribution for 360 ke. V line ( 15. 4. 2010 | MINIBALL Workshop Leuven | IKP Darmstadt | Christopher Bauer )
g factor Limit for g ( ) in 140 Ba is |g|≤ 0. 38 RIV method is applicable But need appropriate calibration isotope(s) 8. 12. 2010 | ISOLDE workshop | TU Darmstadt | Christopher Bauer
Summary Results Conclusions 140 Ba Both methods are complementary to standard MINIBALL experiments Coulex evaluation Lifetime: t = 14(6) ps 12. 5(6) ps 21(9) W. u. 18. 8(9) W. u. Qspec > 0 oblate shape Need extra run with suitable thicker target for DSAM Need extra runs for distribution without RIV method deorientation and with Thank you for your First time tested at REX-ISOLDE calibration isotope(s) 140 Limit for g( )-factor in Baattention! g factor |g|≤ 0. 38 Be aware of contamination! 15. 4. 2010 | MINIBALL Workshop Leuven | IKP Darmstadt | Christopher Bauer
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