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Gamma-ray spectroscopy of excited states in the highly neutron-deficient

Gamma-ray spectroscopy of excited states in the highly neutron-deficient nucleus 158 W. LILIANA DONOSA. Outline. Physics Motivation Technique: Recoil decay tagging Set-up Results. Motivation.

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Gamma-ray spectroscopy of excited states in the highly neutron-deficient

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  1. Gamma-ray spectroscopy of excited states in the highly neutron-deficient nucleus 158W LILIANA DONOSA

  2. Outline • Physics Motivation • Technique: Recoil decay tagging • Set-up • Results

  3. Motivation • Near closed shells angular momentum is generated by aligning the spins of a small number of valence nucleons. • Establishing level schemes allows the specific orbital configurations to be determined. • Tests of shell model predictions. • Difficult to investigate heavy N ≈ 82 nuclei.

  4. Physics Motivation • 2 neutrons far from N= 82 but • 158W has: • - Cross section very low • - Generate a number of reaction • channels in fusion evaporation reaction • - Large γ-ray background • α emitters • - distinct energies • - short half lives • - high decay branching • ratios

  5. Recoil Decay Tagging RITU Dipole Magnet JUROGAM DSSD ϒ ϒ Recoils ϒ Target Primary beam ϒ ϒ ϒ Primary beam (x,y)α Eα tα Eγ tγ Recoils α • (x,y) rec Erec trec

  6. Experimental Set-Up RITU GREAT

  7. 102Pd (58Ni , 2n) 158W* (Ebeam ~ 280 MeV, Ibeam = 6 pna) S. Hofmann et al., Z. Phys. A 333 (1989) 107 S. Hofmann et all, Z. Phys. A. 333, (1989) 107

  8. Isomeric 8+ State • Tagged on isomeric 8+ • state with : Eα = 8280 keV • t1/2 = 0.16 ms

  9. Coincidence Spectrum • γγ coincidance spectra for • 204, 476 or 843 keV • transitions.

  10. Ground State • Alpha tagged single • 158 W (Eα = 6442 keV; t1/2 = 0.9 ms) • Alpha tagged single • 155Lu (Eα = 7390keV; t1/2 = 2.71 ms) • 158W – 155Lu

  11. Level Scheme of 158W • The level scheme of 158W • showing the decay from • the 8+ isomeric state • and the ground state.

  12. Even – Even Systematic • Decrease of the [ν f7/2 h 9/2 ] 8+ state can be understood by interaction of the h 9/2 neutrons • with h11/2 protons, as the π h11/2 subshell is filled.

  13. Experimental Theory - OXBASH

  14. Conclusions • Excited states of 0+ and 8+ states. • Level Scheme of 158W obtained for first time. • Shell model calculation.

  15. Collaborators D.T. Joss, R.D. Page, M.P. Carpenter, D. Seweryniak, J. Simpson, J. Uusitalo, S. Eeckhaudt, T. Grahn, P.T. Greenlees, P.M. Jones, R. Julin, S. Juutinen, H. Kettunen, M. Leino, P. Nieminen, M. Nyman, J. Pakarinen, P. Rahkila, K. Andgren, B. Cederwall, B. Hadinia, C. Ishida, M. Sandzelius,

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