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March 1, 2013GRETINA workshop 20131 Coulomb excitation of even 108-112 Ru and 104-108 Mo isotopes Juho Rissanen Nuclear Structure Group, Lawrence Berkeley National Laboratory

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March 1, 2013GRETINA workshop 20132 COULEX with GRETINA and CHICO2 Highest CARIBU yields at Z≈42,N≈64 in the lower mass region ( 106 Mo) Reaccelerated beams of refractory elements low E(2+) -> high B(E2) -> high Coulomb excitation cross-section Multiple Coulex of Ru/Mo isotopes on heavy target at “safe” energies CHICO2 GRETINA Good Doppler correction -> better energy resolution December 2012

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March 1, 2013GRETINA workshop 20133 Physics motivation, nuclear shapes r-process path Shape evolution vs mass? Variety of different shapes oblate prolate triaxial Shape evolution vs spin? 50 Ru Mo 82 N=64N=66N=68 N=70 ħω=0 ħω=0.2 MeV ħω=0.4 MeV ħω=0.6 MeV 112 Ru Ru isotopes Faisal et al., PRC 82, 014321 (2010)

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March 1, 2013GRETINA workshop 20134 Shape coexistence in Kr isotopes Coulomb excitation of 74,76 Kr beams with 208 Pb target at GANIL at safe energies High-statistics data allows determination of deformation parameters Q and cos(3δ) for different states 74 Kr, 150 hours, 1E4 beam intensity, ≈99% pure Clement, PRC 75, 054313 (2007) θc.m. ≈beta ≈ gamma

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March 1, 2013GRETINA workshop 20135 Summary GRETINA+CHICO+CARIBU allows Coulomb excitation studies of neutron-rich Ru and Mo isotopes Systematic studies of the shape evolution vs. I,Z in the A=110 region (prolate, oblate, shape coexistence, triaxiality) Thanks for your attention What are the experimental limitations? –Beam intensity? With December 2012 performance, 104,106 Mo possible in 12 days of beam time. 3 x increase allows 108 Mo also –Beam purity? How well the impurities are known? –Beam energy, ΔE?

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March 1, 2013GRETINA workshop 20136 Backup slides

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March 1, 2013GRETINA workshop 20137 Analysis Gamma intensities ->CE cross-section Mo and Ru isotopes, level schemes known, some level lifetimes known -> input everything to GOSIA code vary parameters -> try to extract diagonal matrix elements -> static quadrupole moment Q 0 for a given state Rather complete set of matrix elements needed IfIf IiIi MfMf Nuclear reorientation effect dσ/dΩ=f[B(E2),Q], 2 nd order

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March 1, 2013GRETINA workshop 20138 Some mathematics Measurable matrix elements Q is a quadrupole deformation parameter (Bohr’s β) cos (3δ) is a triaxiality parameter (Bohr’s γ)

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March 1, 2013GRETINA workshop 20139 Experiment 106 Mo: B(E2)=1.31 74 Kr: B(E2)=0.84 ->σ( 106 Mo)≈ σ( 74 Kr) x 1.6 Is the mass resolution good enough? Good gamma energy/position resolution needed to tolerate beam impurities ~1 mg/cm 2 thick 208 Pb target factor of 2 down in gamma efficiency More intense beam appreciated to measure several cases / beam time 10 000 counts in photopeak needed

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March 1, 2013GRETINA workshop 201310 Beam time days Factor of 2 down in gamma efficiency 10000 counts in a photopeak Isotopeσ CE vs KrBeam vs KrBeam time days 108 Ru1.20.812.5 110 Ru1.31.56.7 112 Ru1.40.426 102 Mo1.10.257 104 Mo1.61.26.5 106 Mo1.61.45.7 108 Mo1.90.235

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March 1, 2013GRETINA workshop 201311 Other examples Q, cos 3δ vs mass Q, cos 3δ vs spin Cline Ann. Rev. Nucl. Part. Sci. 36, 683 (1986) g.s. band γ band 0 + 2 band0 + 3 band

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