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Nuclear structure observables

Nuclear structure observables. Nuclear structure observables. Number of nuclei required. ~ 10 1 - 10 3. particle stability, limits of existence. ~ 10 3. isotopic mass, decay properties, half-life

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Nuclear structure observables

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  1. Nuclear structure observables Nuclear structure observables Number of nuclei required ~ 101 - 103 particle stability, limits of existence ~ 103 isotopic mass, decay properties, half-life Example : vanishing N = 20, 28 magic numbers in Z = 11 and Z = 16 from DE2n in neutron rich P, S, and Cl > X · 103 nuclear spins, nuclear moments (ground states) > 104 /s g spectroscopy, excited states, spins, parities etc. > 105 /s nuclear moments of excited states (100fs <t < 10ps) The measurement of magnetic moments comes at the end, when other properties have been studied already. But, can they still reveal new aspects ?

  2. g factor measurements of shortlived states at radioactive ion-beam facilities g factor measurements of shortlived states at radioactive ion-beam facilities

  3. Physics Motivation Physics Motivation B(E2) anomaly in 136Te Exp. and theoretical g(2+) in Te the isotopes 136Te  Te  136Te N. Benczer-Koller et al., PLB 664(2008)241 D.C. Radford et al., Phys. Rev. Lett. 88 (2002) 222501

  4. + g(2 ) in 138Xe with p(1g7/2)-² + n(2f7/2)²configuration ? 1 Comparison to Xenon isotones Comparison to Xenon isotones A A Te Xe 54 N 52 N ? + + B(E2,2 0 ) 16 1 1 ] . u 14 . W [ 12 ) 1 + 0 10 8 + 1 2 , 2 6 E ( B 4 2 0 + g(2 ) 1 0,8 gschmidt 0,6 r protons neutrons o 0,4 t c a f 0,2 g g7/2 2f7/2 - 0.547 + 0.491 0 2d5/2 + 1.917 -0,2 + 0.083 2d3/2 -0,4 132 134 136 A = 134 136 138 + 1.417 h11/2 C 65 exp.: G.Jakob et al., Phys.Rev. (2002) 024316 calc.: J.Terasaki et al., Phys.Rev. C 66 (2002) 054313 N. Benczer-Koller et al., Phys.Lett. B 664 (2008) 241 D.C. Radford et al., Phys.Rev.Lett. (2002) 222501 A. Stuchbery, N. J. Stone, Phys. Rev. C 76 (2007) 034307

  5. REX-ISOLDE experiment IS415 REX-ISOLDE experiment IS415 90o Detector +Q  0o Strahl E2  q -Q Beam Detector   N(+Q) N(-Q) r = N(+Q) N(-Q) W(Q) -Q +Q angleQ [degree]

  6. Si part: PIN diodes

  7. REX-ISOLDE experiment IS415 REX-ISOLDE experiment IS415 „Cleaning up“ the g spectra find physical events look for particle- g concidence gate on particles time gate on true events random substraction

  8. REX-ISOLDE experiment IS415 REX-ISOLDE experiment IS415 Experimental results particle – g - angular correlation nuclear spin precession Fexp = 23(31) mrad G*F(lin)/g = 78.4 mrad g(2 )exp = + 0.31(39) g(2 )theo = + 0.29 (QRPA) g(2 )theo = + 0.4 (G-matrix) + 1 + 1 + 1

  9. Results and discussion Results and discussion Te isotopes Xe isotopes experimental g(2+) of 138Xe in agreement with theory uncertainty too large for detailed studies (neutron dominance in 136Te still not proofed) more experimental data in this mass region required Accuracy has to be improved in future campaigns !

  10. Restrictions and constraints Restrictions and constraints Main constraints at REX-ISOLDE for TF measurements: annular Si detector or rect. Si above and below beam axis • straggling of the scattered beam in • the very thick target (>8 mg/cm2) • time structure of the beam Faraday-cup Beam straggling θmin Q > 20° 3.8x10-3 light target target ion Gd Cu Ta projectile For a beam intensity of 2x106 ions/s: 7600 beam ions/s with θ > 20° 5 Hz, 700 μs: 7600 beam ions in 3500 μs, = 2 beam ions / μs -- on average !

  11. Solutions for future campaigns Solutions for future campaigns Solution 1 : lighter beam ions For a beam intensity of 2.2x106 ions/s: 72Zn @ 2.8 MeV/u 50 beam ions/s with θ > 20° Target: 27Al – Gd – Ta -- Cu 1.1 + 4.0 + 1.0 + 3.5 mg/cm2 13 Hz, 300 μs: 50 beam ions in 3900 μs, that is one beam ion every 80 μs -- on average ! Much better than 2 ions / µs ! However, in case an absorber foil has to be used 15 MeV 20° < θ < 36° Still an acceptable situation ! As slow extraction as possible is crucial for us !

  12. From REX-ISOLDE to HIE-ISOLDE From REX-ISOLDE to HIE-ISOLDE REX-ISOLDE - 2.78 MeV/u HIE-ISOLDE - 3.73 MeV/u without Ta without Ta with Ta with Ta integral cross section increase of integral cross section over recoil detection range by a factor 4-5 ! larger recoil velocities stronger transient fields larger effects ! TF g-factor measurements will clearly benefit from the increased beam energies available at HIE-ISOLDE !

  13. Summary Summary still no verified explanation for B(E2) reduction in 136Te first g factor measurement at REX-ISOLDE using the low-energy transient field technique significantly improved experimental conditions for TF measurements in + 138Xe : g(2 ) = 0.31(39) 1 ions up to A ~ 140 (HIE-ISOLDE) ions up to A ~ 80 (REX-ISOLDE)

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