Shell-model calculations of psd-shell nuclei Furong Xu

School of Physics, Peking University

I. Introduction

II. Shell-model calculations

1. The role of nn interaction and configuration mixing in

N=14 and 16 shell evolutions;

2. Increase model space with fitting a new effective

interaction

III. Summary

I. Introduction

N=16

N=14

T. Otsuka et al., PRL 105, 032501 (2010)

8

6 6

16

14

8

0d3/2

0d5/2

0d3/2

0p3/20p3/2

0p1/2

1s1/21s1/2

0d5/2

0p1/2

proton neutron

2+

2+

R.V.F. Janssens, Nature 459, 1069 (2009)

R. Kanungo et al., PRL 102, 152501 (2009)

C.R. Hoffman et al., PLB 672, 17 (2009)

Shell-model calculations are very dependent on interactions used!

Doubly magic nature of 24O

T. Otsuka et al., PRL 105, 032501 (2010)

8

6 6

1614

8

0d3/2

0d5/2

0d3/2

0p3/20p3/2

0p1/2

1s1/21s1/2

0d5/2

0p1/2

proton neutron

Experiments: 0d3/2 neutrons unbound in C, N, O

0d3/2

1s1/2

C.R. Hoffman et al., PRL 100, 152502 (2008)

Unbound

II. Shell-model calculations

1. N=14 and 16 shell closures

Otsuka et al., PRL 87, 082502 (2001).

C.X. Yuan, C. Qi, F.R. Xu, NPA 883, 25 (2012)

+ =0+

+ =2+

core coreV j=0= -2.82MeV V j=0= -2.12MeV

core coreV j=2= -1.00MeV V j=2= -0.82MeV

Interaction matrix elements of couplings Vj=0 and Vj=2

8

6 6

16

14

8

0d3/2

0d5/2

0d3/2

0p3/20p3/2

0p1/2

1s1/2 1s1/2

0d5/2

0p1/2

proton neutron

repulsive tensor

repulsive spin-orbit

attractive tensor

The neutron-proton interaction reduced when going from oxygen to carbon

attractive 5/2 5/2

nnd dV

T. Otsuka et al., PRL 95, 232502 (2005)

attractive , important!

22O: small effect

20C: big (1s1/2 and 0d5/2 degenerate)

1/2 1/2

nns sV

6 6

16

14

8

0d3/2

0p3/20p3/2

0p1/2

1s1/2

0d5/2

0p1/2

proton neutron

repulsiv

e LS

attractive tensor8

C.X. Yuan, C. Qi, F.R. Xu, NPA 883, 25 (2012)

C, N, O wave-function analysis for g.s.

core

coreN=14

N=14

Excited configurations are more important in C isotopes

p n

16

14

14

16

+3/2+ 3/2+

core core

N=11 isotones: 5/2+, 3/2+ inversion related to N=14 shell

From Paul Fallon at LBNL

Carbon

WBT

(2009): Z. Elekes et al., PRC 79, 011302 (R)

(2011): M. Petri et al., PRL 107, 102501

Calculation is sensitive to effective charges used.

21( 2; )2 1i f p p n n

i

B E j j e A e Aj

Ap, An: shell-model quadrupole transition matrix elements.

C isotopes

The effective charges taken from: H. Sagawa et al., PRC 70, 054316 (2004)

The gap is reduced with increasing neutrons on 0d5/2.

This increases the proton excitation.

WBT0hω

attractive tensor

Generally agree well, but still model dependent!

1. Increase model space;

2. Improve interaction.

Our new effective interaction for 0-2 hω

N=11 isotones

III. Summary

1. The nn interaction and configuration mixing

play also important roles in shell evolutions of

N=14, 16.

2. Large model space and suitable effective

interaction are important factors as well.

Collaborators:

C.X. Yuan

C. Qi

T. Otsuka

T. Suzuki

X.B. Wang

N. Tsunoda

Thank you!

NN2012San Antonio, Texas

29 May, 2012