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Introduction Calculations for the N=7 isotones Summary

Deformation effects on the structures of the N=7 halo nuclei Furong Xu, Junchen Pei School of Physics, Peking University. Introduction Calculations for the N=7 isotones Summary. I. Introduction. Parity inversion. H.D. Wilkinson and D.E. Ablburger, Phys. Rev. 113, 563 (1959);

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Introduction Calculations for the N=7 isotones Summary

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  1. Deformation effects on the structures of the N=7 halo nucleiFurong Xu, Junchen PeiSchool of Physics, Peking University Introduction Calculations for the N=7 isotones Summary

  2. I. Introduction Parity inversion • H.D. Wilkinson and D.E. Ablburger, Phys. Rev. 113, 563 (1959); From the observedβdecay of 11Be, the nucleus might have an ½+ ground state. • In the next year, Talmi and Unna demonstrated that this possibility with shell-model systematics; • Later on, the levels of ½+ and ½- states were well established experimentally. e.g. J.P. Deutsch et al., PLB 268, 178 (1968)

  3. mean-field scheme of neutron levels ½+[211] 2s1/2 5/2+[202] 1d5/2 ½+ 3/2+[211] N=8 ½+[220] ½- 1p1/2 ½-[101] 3/2-[101] 1p3/2 ½-[110] β2=0.3

  4. In 1991, reaction cross section of 11Be was measured to suggest neutron-halo; M. Fukuda et al., PLB 268, 339 (1991) • Parity inversion ( ½+, ½-), halo structure, very strong E1 transition from ½- to ½+ states. interesting! • In the past ~15 years, a lot of works on 11Be; Projected Hartree-Fock, Skyme-Hartree-Fock, Variational shell model, coupled channel, RMF…

  5. Variational shell model (configuration mixing calculations) T. Otsuka, N. Fukunishi, H. Sagawa, PRL70, 1385(1993) Mean field valid? very large β2 deformation? 10Be, β2 ~ 0.67 from B(E2, 2+→0+)=52 (6) e2fm2 ?

  6. II. Investigation of the N=7 isotones

  7. Deformed SHF with the adiabatic blocking of the odd neutron. • Blocking ½+ [220] (the lowest level in sd shell) ½+ • Blocking ½-[101] (the highest level in p shell) ½-

  8. surface pairing volume-pairing mixture-pairing Surface pairing component is important for exotic nuclei J. Dobaczewski et al., EPJA 8, 59 (2000).

  9. SHF without pairing X.Li and P.-H.Heenen, PRC 54,1617(1996) Very flat minima very soft shapes

  10. 晕态

  11. Deformations All ½- states have spherical shapes; For the ½+ state: 11Be: β2 ~ 0.98 13C: β2 ~ 0.5 15O: β2 ~ 0.0 9He: Very soft shapes Significant vibrational effect; Core-vibration mixture; Energy could be sensitive to the effects, but density would not

  12. To understand halo structure: Calculate <l2> If 1d5/2 (l=2), <l2>=6, halo? 9He 11Be 13C <l2>: 0.2 2.6 3.7 mixture of 2s1/2 halo

  13. mean-field scheme of neutron levels ½+[211] 2s1/2 5/2+[202] mixing 1d5/2 ½+ 3/2+[211] N=8 ½+[220] ½- 1p1/2 ½-[101] 3/2-[101] 1p3/2 ½-[110] β2=0.3

  14. Glauber-model calculations of cross sections for 11Be (1/2+) 33 A MeV Expt.Cal.11Be+12C1.561.98311Be+27Al2.272.73413C+12C1.361.43413C+27Al1.911.717790 A MeV11Be+12C0.9421.15611Be+27Al1.381.68

  15. Summary • For N=7 isotones, the ½＋state may polarize the nuclei to be largely deformed. • Mean-field calculations cannot understand the parity inversion that would be beyond mean field. • Other properties, such as halo structure, can be obtained by mean field models. To be published in Nucl. Phys. A

  16. Thank you

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