Clusterlike correlations in light nuclei

1
Cluster-like correlations in light nuclei

• N. Itagaki (University of Tokyo)

2
gas like structure
Excitation energy
cluster-threshold
mean-field, shell structure (liquid)
3
New phase geometric cluster structure
stabilized by adding neutrons
14C
gas like structure
athreshold
Excitation energy
cluster state with geometric shape
mean-field, shell structure (liquid)
N. Itagaki, T. Otsuka, K. Ikeda, and S. Okabe,
PRL 04 (2004) 142501
4
10Be
Sigma orbit
5
The series cluster structure stabilized by two
neutrons(2alpha2n, 3 alpha2n) in 18O

• It is well known that one of the three 0 states
  is missing in the shell models if we assume the
  p-shell closed configuration for 16O
• From the cluster model side, 14Calpha models
  have been introduced, and although the calculated
  energy is very high (Ex 8-9 MeV) , the
  calculated 0 state has been assigned to the
  second 0 state by comparing with the B(E2) values

6
COSM --- H. Masui et al. Phys. Rev. C 75,
034316 (2007) GSM ----- N. Michel et al.
Phys. Rev. C 67, 054311 (2003)
7
(No Transcript)
8
Our study

• We study whether neutrons in the middle of the
  nucleus bind four alpha clusters with tetrahedron
  configuration
• S2 configuration of the neutrons requires the
  particle-hole excitation of the 16O core, and we
  may obtain three 0 states in low-lying energy
  region with reasonable excitation energy
• 14Calpha model space is also introduced

9
18O
16Onn
14Calpha
10
(No Transcript)
11
22Ne
16Oalphann
18Oalpha
12
22Ne
01
02
03
13
AMD calculation corresponding state Ex 7 MeV as
the second 0 state
In our case, nodes and the density distribution
along alphaO axis are automatically created
by the antisymmetrization effect
14
Another exmaple of geometric cluster structure
stablized by the neutrons ? linear chain
16C
Kp1-
Kp1
Kp0
Kp0
Kp2
15
Properties
Stability against bending motion
Solid 16C Dotted 20C
16
gas like structure
Excitation energy
cluster-threshold
cluster structure with geometric shape (solid)
mean-field, shell structure (liquid)
17
(No Transcript)
18
One of the merit of THSR wave function we can
introduce size of the cluster state
We simplify the THSR wave function

• We need to study multi-alpha cases
• We need to study the case with core nuclei
• The coupling with normal states should be
  included
• Di-neutron condensate around the core can be
  studied

19
Virtual THSR wave functionN. Itagaki, M.
Kimura, M. Ito, C. Kurokawa, and W. von Oertzen,
Phys. Rev. C 75, 037303 (2007)
For the aclusters in the condensed state
20
3a
2a
Sigma 5 fm
Sigma 2 fm
Solid, dotted, dashed, dash-dotted ? s 2,3,4,5
fm
r.m.s. radius of 12C
21
20Ne 5 alphas
Sigma 4 fm
Sigma 3 fm
Sigma 2 fm
N. Itagaki, Tz. Kokalova, M. Ito, M. Kimura, and
W. von Oertzen, Phys. Rev. C 77 037301 (2008)
22
0 states of the 5a system (20Ne)
16Oalpha 5alpha cond.
16Oalpha
23
(No Transcript)
24
Alpha-gas state around core nucleus
Study of the Hoyle state, the next step..
Tz. Kokalova et al. Eur. Phys. J A23 (2005)
28Si24Mg ? 52Fe
Enhancement of emissions of the condensed state
from the compound state compared with the
sequential a emissions
25
6-alpha gas-like state

• s 3 fm

26
6-alpha gas-like state
Dotted line Around 16O

• s 3 fm

27
6-alpha gas-like state
Dotted line Around 16O
Dashed line Around 40Ca

• s 3 fm

28
Di-neutron correlation in 8He?

• 8He is well-bound compared with 6He and 11Li
• Sub-closed configuration of spin-orbit-favored
  shell

Di-neutron ? no spin-orbit
Condensation of S0 di-neutron clusters components
really contributes?
29
4He4n model space (AMD)
8He 0
Alphannnn
N. Itagaki, M. Ito, K. Arai, S. Aoyama and Tz.
Kokalova Phys. Rev. C 78, 017306 (2008).
30
s 1fm
s 2 fm
s 3 fm
s 4 fm
s 5 fm
Alphannnn
8He 0
4He2 di-neutron clusters
31
B H 0 case
32
In 7H case
S. Aoyama and N. Itagaki (2009)
33
Summary

• Cluster structure stabilized by the valence
  neutrons shown in 2alpha2n and 3alpha2n is
  extended to 4alpha2n and 5alpha2n cases
• The study on gas-like cluster states can be
  extended to heavier systems (with/without core)
  using Monte Carlo Technique
• Competition between shell and di-neutron
  structure can be investigated

34
Gas-like state of 3 alpha around 40Ca

• s 3 fm

35
Determined to reproduce the alpha-alpha and
alphaN Phase shifts
36
(No Transcript)
37
Is it due to the lowing of the Coulomb barrier
for the condensed state?
Tz. Kokalova, N.Itagaki., C. Wheldon, and W von
Oertzen, Physical Review Letters 96, 192502
(2006).