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In-Beam Observables Rauno Julin Department of Physics University of Jyväskylä JYFL Finland

In-Beam Observables Rauno Julin Department of Physics University of Jyväskylä JYFL Finland. In - Beam. p. γ. α. n. γ. p. Combination of In-Beam and Delayed Events. . . . . .  , p, β , … e − , . Focal plane Detectors. Beam. Ge Array. Separator. p rompt

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In-Beam Observables Rauno Julin Department of Physics University of Jyväskylä JYFL Finland

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  1. In-Beam Observables Rauno Julin Department of Physics University of Jyväskylä JYFL Finland

  2. In - Beam p γ α n γ p

  3. Combination of In-Beam and DelayedEvents      , p, β, … e−,  Focalplane Detectors Beam GeArray Separator prompt events =In-Beam Data Readout tagged with Best resolution in gamma-ray spectroscopy delayed events

  4. Example: In-beam probing of Proton-Drip Line and SHE nuclei very neutron deficient heavy nuclei can be produced via fusion evaporation reactions cross-sections down to 1 nb  short-living alpha or proton emitters → tagging methods Nb Pb Sn

  5. levelenergies, transitionmultipolarities, spins, parities

  6. Yrast vs. non-Yrast Close to the valley of stability: Allknownenergylevels in 116Sn Farfromstability: Only a verylimited set of levelsclose to the yrastlinecanbeseen

  7. Example: in-beamspectroscopy at the extreme - 180Pb α-α tagged singles in-beam γ-ray spectrum 92Mo(90Zr,2n)180Pb, 10 nanobarn 4+ → 2+ 6+ → 4+ 2+ → 0+ 8+ → 6+ P. Rahkila et al. Phys. Rev. C 82 (2010) 011303(R)

  8. Energy-level systematics: Pb - isotopes Prolate Oblate 186Pb104 Level systematics of even-A Pb nuclei Spherical Prolate Oblate Spherical 180Pb N = 104  Verification of shapecoexistence

  9. Energy-levelsystematics vs. Ground - stateradia Prolate 6p-4h Spherical 0p-0h Oblate 4p-2h • Understanding of ground-state • properties

  10. Odd-Anuclei: Informationaboutorbitals and deformation

  11. Verification of prolate shape in 185Pb Coupling of the i13/2neutron ”hole” to the prolatecore Stronglycoupledband

  12. Energy – levelsystematics: Coulomb-EnergyDifferences T = 1 band 2+ A=66 is the heaviest triplet of T = 1 bands up to 6+ 66Se32 4+ 6+ N = Z TED=Triple Energy Differences TED = Ex(Tz= -1) + Ex(Tz= +1) - 2 Ex(Tz= 0) V = vpp + vnn - 2vpn Chargeindependence One-bodytermscancel out Isospinnon-conservingcontribution is needed !

  13. moment of inertia

  14. Basics Kinematicalmoment of inertia Dynamicalmoment of inertia = arithmeticalaverage of over Quantalsystem Measured

  15. J vs. deformation Quadrupoledeformedrigidrotor  notmuchdependent on deformation ! ~ SD band in 152Dy ~ SD band in 193Bi ~ fission isomer in Pu Fluid  stronglydependson deformation !

  16. Example: Nobelium region J(1)  no Z = 104 shellgap Whyare254No and 256Rf almostidentical ?

  17. Calculations

  18. Example: Coexisting shapes in light Pb region Rigid: J(1)~ 1 + 0.3β Hydrodynamical: J(1)~ β2 → Need B(E2) , Qt PROLATE OBLATE J(1)(rig)= 110

  19. Subtracting a reference details Alignments: 180Pb behaves like 188Pb → Mixing with oblate structures 180Pb

  20. Subtracting a reference details Alignments near N =104: Open symbols – Hg’s Filled symbols – Pb’s  Why Pb’s more scattered ?

  21. levellifetimes, transitionrates, quadrupolemoments, deformation

  22. Basics Quadrupole deformed nucleus:

  23. In-beamlifetimemeasuremets • Recoil distance Doppler-shift (RDDS) lifetime measurements (plunger). • Combined with selective recoil-decay tagging method.

  24. Example: Lifetimes for shape coexisting levels in light Pb’s and Po’s ... for 194Po196Po 186Pband 188Pb │Qt│ Pb: │Qt│ → │β2 │ = 0.29(5) for the ”pure” prolatestates • Po: • │Qt│ → │β2 │ = 0.17(3) • for the oblatestates • the groundstate of 194Pois a pure • oblate 4p-2h state ? J(1)

  25. Exp vs. Theory Beyond-mean-fieldcalculationsbyM. Benderet al. vs. the exp. data Theor. Theor. Exp

  26. Example: Collectivity of the intruder bands in light Pt, Hg and Pb nuclei J(1) identical for prolate intruder bands in N ~ 104 Pt, Hg and Pb ⇒ identical collectivity (Qt)?

  27. Collectivity of the intruder bands in light Pt, Hg and Pb nuclei prolate oblate Is the collectivityreallydecreasing with decreasing Z ?

  28. Example: Experimental difficulties Testing the simple seniority picture: B(E2)-value systematics, N=122 2 8+ 2 6+ 2 4+ Δν=0 2 2+ Δν=2 0 0+ ν 8+ is long living  impossible to determine the lifetimes of the 6+, 4+ and 2+ members of the multiplet

  29. Comment Mass systematics vs. shape coexistence

  30. Two-neutron separation energy systematics Pt Scale !! Hg Why the smooth behaviour at N = 104 ?

  31. Other mass filters needed to see the deviations Hgisotopes ∆4

  32. Comment Interpretation of E0 transitionrates

  33. Example: 2neutron-2 hole intruders on the island of inversion • Interpretation: • Weakmixing ( 10/90) between the spherical 0+state and • the deformed 2neutron-2hole intruder 0+state (ß = 0,27) • Comment : • = 8.7 × 10-3 is a smallvalue for an E0 transition in lightnuclei • Doesitmakesense to applysuch a simplemodel for such a weak E0 ?

  34. Example: 2neutron-2 hole intruders on the island of inversion The simpletwo-levelmixingmodel: !!  Simpleshell-model: = 40 × 10-3 (A=44) ”Single-particle” value: (= E0 connecting 50/50 mixed 0+statesinvolving2 protonsoccupying orbitalsfromdifferentoscillatorshells ) E0’s involvingneutronexcitations : (if no state-dependentmonopoleeffectivecharge for neutrons)

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