1. 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

2. I. Introduction H.D. Wilkinson and D.E. Ablburger,
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).

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

13. 晕态

14. All ½- states have spherical shapes; For the ½+ state: 11Be: β2 ~ 0.98
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

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

16. 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

17. Glauber-model calculations of cross sections
for the 1/2+ state
33 A MeV Expt. Cal. 11Be+12C Be+27Al C+12C C+27Al A MeV 11Be+12C Be+27Al

18. 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.

19. Thank you