Introduction Calculations for the N=7 isotones Summary
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Deformation effects on the structures of the N=7 halo nuclei Furong Xu, Junchen Pei School of Physics, Peking University I. Introduction II.Calculations for the N=7 isotones III.Summary
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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); - PowerPoint PPT Presentation
Transcript of 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
I. Introduction
II. Calculations for the N=7 isotones
III. Summary
I. IntroductionH.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 establi
shed experimentally.
e.g. J.P. Deutsch et al., PLB 268, 178 (1968)
Parity inversion
mean-field scheme of neutron levels
2s1/2
1d5/2
1p1/2
1p3/2
N=8
β2=0.3
½+[211]
5/2+[202]
3/2+[211]
½+[220]
½-[101]
3/2-[101]
½-[110]
½-
½+
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…
(1/ 2)1 1/ 2 2 5/ 2
1| 0 | 2 [2 |1 ]2 c v c vs d
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 ?
II. Investigation of the N=7 isotones
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-
surface pairing
volume-pairing
mixture-pairing
Surface pairing component is important for exotic nuclei
J. Dobaczewski et al., EPJA 8, 59 (2000).
•
SHF without pairing
X.Li and P.-H.Heenen, PRC 54,1617(199
6)
Very flat minima very soft shapes
•
2 3 4 5 6 7 8
-8
-6
-4
-2
0
(1/2)+ levles of N=7 nuclei
expt.
MeV
Z
晕态
Significant vibrational effect;Core-vibration mixture;Energy could be sensitive to the effects, but density would not
Deformations
All ½- states have spherical shapes;
For the ½+ state:11Be: β2 ~ 0.9813C: β2 ~ 0.515O: β2 ~ 0.0
9He:
Very soft shapes
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
mean-field scheme of neutron levels
2s1/2
1d5/2
1p1/2
1p3/2
N=8
β2=0.3
½+[211]
5/2+[202]
3/2+[211]
½+[220]
½-[101]
3/2-[101]
½-[110]
½-
½+
mixing
33 A MeV
Expt. Cal.11Be+12C 1.56 1.983 11Be+27Al 2.27 2.734 13C+12C 1.36 1.434 13C+27Al 1.91 1.717
790 A MeV 11Be+12C 0.942 1.156
11Be+27Al 1.38 1.68
Glauber-model calculations of cross sections
for 11Be (1/2+)
Summary
• For N=7 isotones, the ½ ＋state may polari
ze the nuclei to be largely deformed.
• Mean-field calculations cannot understan
d the parity inversion that would be beyon
d mean field.
• Other properties, such as halo structure, c
an be obtained by mean field models.
To be published in Nucl. Phys. A
Thank you
