# Presentation: 858675

## Proton single-particle states in neutron-rich nuclei

- CNS, University of Tokyo
- S. Shimoura

## Studies of Neutron/Proton-rich nuclei

- Size/-distribution
- Skin/Halo
- Shell Structure
- New magic #
- Single particle leveles
- Isospin / Deformation
- New modes
- IVE1
- ISE0, ISE1
- etc.

- Direct Reactions

- Size/-distribution
-  R, elastic scat.
- Shell Structure
- Mass / Sn, S2n
- Inelastic scatt.
- Low lying states
- Knockout / Transfer
- New modes
- Coulex
- Inelastic scatt.
- CEX
- etc.

- Mean field / Correlation ...

## Introduction

- Structure information of nuclei as functions of N and Z – Shell Evolution...
- Collectivities / Single particle structure in excited states

**Disappearance of N=8 magicity**

**Disappearance of N=20 magicity**

**Deformation / Cluster structure**

**Nuclear responses**

- 12Be

- 22O

## Heavy Nuclei: Strong Coulomb Field
Coulomb Excitation, Coulomb Dissociation
E1, E2, (M1) / Isovector
H, D, 4He [Liquid targets]
Inelastic Scattering
Isovector (H) / Isoscaler(H, D, 4He)
Spin-Flip (H, D) / Spin-Non-Flip (H, D, 4He)
Charge Exchange
Fermi type (H) / Gamow-Teller type (H, D)
Nucleon Transfer
(,t), (,3He) Reaction
Knockout
Other (Be, C, ...)
Inelastic Scattering
Knockout / Fragmentation

- Coulomb Excitation, Coulomb Dissociation
- E1, E2, (M1) / Isovector
- H, D, 4He [Liquid targets]
- Inelastic Scattering
- Isovector (H) / **Isoscaler**(H, D, **4****He**)
- Spin-Flip (H, D) / **Spin-Non-Flip** (H, D, **4****He**)
- Charge Exchange
- Fermi type (H) / Gamow-Teller type (H, D)
- Nucleon Transfer
**(********,t), (********,****3****He)** Reaction
- Knockout
- Other (Be, C, ...)
- Inelastic Scattering
- Knockout / Fragmentation

- Probes for direct reactions

- Same Nucleus can be populated via Different Processes without changing Detector System

- Dirty RI beams and/or
- Changing Target

## Nucleon Transfer from 4He @ several tens of  MeV per nucleon

- Proton Single particle statesin neutron-rich nuclei
**4****He(****12****Be,****13****B********)**
- 		[S. Ota et al., Phys. Lett. B 666 (2008) 311]
**4****He(****22****O,****23****F********), **[4He(23F,23F),** **4He(24F,23F),** **He(25Ne,23F)]
- 	utilizing cocktail beams
- 		[S. Michimasa et al., Phys. Lett. B 638 (2006) 146]

- p

- n

## Nucleon (Proton) Transfer from Alpha

- (d,n), (3He,d), (,t), ...

- Incident energy higher than few tens of MeV/u
- Thicker target (100~200 mg/cm2)
- Less distortion effect
- Less multi-step process
- Same optical potential as inelastic excitation
- Identification by comparing with other direct reactions
-   But
- Momentum mismatch

## Momentum Matching Condition (Classical)

- As if “Getting off from the moving train (projectile) to platform (target)”
- Internal motion in the train (Fermi motion in the projectile) along the opposite direction of the train (target)
- Motion on the platform (Fermi motion of the nucleon on the target) along the direction of the train

## a

*a*

*B*

*x*

*A*

*b*

***r****c*

***r****c’*

***r****xA*

***r****xb*

- Same value but different expressions

- Fourier Components of wave functions of nucleon (*x*) in *a* and *B*

- Plane Wave Born Approx.

- Binding energies of *a* and *B*

- Momentum Matching Condition (QM)

## Proton Transfer in Momentum Space

- 12Be(d,n) @ 50 A MeV

- 12Be(,t)
- @ 50 A MeV

**E****x****=0**

**E****x****=40**

**E****x****=0**

**E****x****=40**

**12****Be**

**12****Be**

**d**

**p**

**13****B*****(10MeV)**

**n**

**p**

**13****B*****(10MeV)**

****

*q*z (fm-1)

*q*z (fm-1)

- 1

- 0

- -1

- -2

- 0

- 1

- 2

**t**

- 1

- 0

- -1

- -2

- 0

- 1

- 2

*q* (fm-1)

*q* (fm-1)

**13****B***

**d**

**13****B***

****

## DWBA Calculation

- Example:
- 	22O(,t)23F
- 	22O(d,n)23F

## 13B 

**N-rich N=8 Nuclei**

- Spin-orbit splitting between p1/2 & p3/2 depend on the number of protons in p3/2 orbit attracting p1/2 orbit

- 8

- p3/2

- p1/2

- sd

*V*

- n-rich
- Beryllium

- n-rich
- Boron

- p

- n

- p

- n

- p3/2

- p1/2

- Change of Boron Proton Shell
- as a function of configuration

- 13Bgs

- 13B*

**13****B**** **
**Spherical ground state**
**How about excited states?**
**Deformed core + proton?**

- sd

**12****Be**
**Low-lying 2****+**** state**
**Low-lying 1****-**** state **
**Low-lying 0****+****2**** state**
**   ****Magicity loss in N=8**
**   ****Neutron intruder configuration**
**   ****Deformed**** ground state**

- p3/2

- p1/2

- sd

- p

- n

- p

- n

- p3/2

- p1/2

- sd

- Deformed mean field?

- 6

- Proton intruder state

**Notes:**
In the region 
where a proton affects sensitively
neutrons’ structure,
Do protons’ structure change or not?

At first, I talk about the motivation for the experiment.
The new magic number at N=16 region is interesting.
Stability of Oxygen and  Fluorine is quite different.
Neutron drip line of Oxygen is at N=16, on the other hand, neutron drip line of Fluorine is over 20.
As the reason, it is suggested that the ninth proton in d5/2 strongly attracts valence neutrons in d3/2.

This result indicates that for understanding shell evolution in exotic isotopes,
investigation on p-n interactions is important.

## Spectra of 14C, 12Be, 11B, and 13B

*S**n*=4878

- 14C

- 0+

- 1-

- 0+

- 2+

- 6094

- 6589

- 7012

- 12Be

- 0+

- 1-

- 0+

- 2+

- 2700

- 2240

- 2100

- 11B

- 13B

- +

## 4He(12Be,13B) @ 50 A MeV

- [220]1/2

- 8

- C2S(BM) ~ 0.27
- 	for =0.4
- (12Be(p,p’)) ~ 0.6-0.7

- Spherical G.S.
- Deformed Excited 1/2+ ?

- 2 ~  ~ 0.95

- 0.3

- [110]1/2

- [101]3/2

- [101]1/2

- Deformed 12Be core + 1 proton ?

## 4He(12Be,13B) @ 50 A MeV

**4****He(****12****Be,****13****B********) @ 50 *****A***** MeV**

- 4.83 MeV states strongly excited

- 12Be beam

**CNS GRAPE**

- NaI(Tl) array

- Liq. He target

## 4He(12Be,13B) @ 50 A MeV

- Angular Distribution of 13B coin. with **4829** keV 

- FR-DWBA (DWUCK5)
- Optical Potential:
-      12C + 4He (entrance)
-    12C + 3He (exit)

- L=0 -> J  = 1/2+

- C2S ~  0.2
- -> Proton “single particle” state on 12Be

## 4He(12Be,13B) @ 50 A MeV

- Proton “single particle” state on 12Be

**3/2-**

- 1/2+ : 0.01

- 5/2+

- 3/2+

**3/2- : 0.15**

- 1/2+ : 0.03

- 1/2+ : 0.003

**1/2+ : 0.30**

**1/2- : 0.87**

- PSDFU

- PSDFU

- ?

- ?

- Shell model (3hw)

- ?

## -

**+**

**+**

**α**

**α**

**13****B(1/2****+****1****)**

- Present calc.

- Hyper deformation ?

- proton

- neutron

- 4He(12Be,13B) Experiments
- By Ota et al.

- By Kanada-Enyo

## Exotic Magic Number at N=16 (Z~8)

**Exotic Magic Number at N=16 (Z~8)**

- Spin-orbit splitting between d3/2 & d5/2 depend on the number of protons in d5/2 orbit attracting d3/2 orbit by *V*

- 16

- 20

- d5/2

- d3/2

- s1/2

*V*

- n-rich
- Oxygen

- n-rich
- Fluorine

- p

- n

- p

- n

- d5/2

- d3/2

- s1/2

**Notes:**
In the region 
where a proton affects sensitively
neutrons’ structure,
Do protons’ structure change or not?

At first, I talk about the motivation for the experiment.
The new magic number at N=16 region is interesting.
Stability of Oxygen and  Fluorine is quite different.
Neutron drip line of Oxygen is at N=16, on the other hand, neutron drip line of Fluorine is over 20.
As the reason, it is suggested that the ninth proton in d5/2 strongly attracts valence neutrons in d3/2.

This result indicates that for understanding shell evolution in exotic isotopes,
investigation on p-n interactions is important.

## 23Fspectra

- 23Fspectra

- S. Michimasa et al., Phys. Lett. B 638 (2006) 146

- +1p

- Inel.

- -1n

- -1n1p

- Data are taken simultaneously

## 22O(a,t)23F*

- 22O(a,t)23F*

- S. Michimasa et al., Phys. Lett. B 638 (2006) 146

## d5/2 full

- S. Michimasa et al., Phys. Lett. B 638 (2006) 146

- d5/2 full

- d5/2 empty

## Summary

- Nucleon transfer reactions (,t) above several tens of A MeV are demonstrated for proton single-particle states in n-rich nuclei
- Structure change in excited state
- Proton intruder states in 13B
- Effective SO splitting in 23F
- Future @ RIBF :
- 	SHARAQ spectrometer and gamma-detector GRAPE will be used for studies at heavier exotic nuclei

## GRAPE

**Project**

- Grant-in-Aid of MEXT

***UT******Sakai-G***

***RIKEN***

- SHARAQ

- High resolution missing mass
- p/p=1/15000

- High resolution
- - spectroscopy
- E/E=1/100
- (Doppler Correction)

## Collaborators

- CNS / Univ. Tokyo
- M. Niikura, M. Tamaki, S. Ota, A. Saito, T. Fukuchi*, E. Ideguchi, M. Notani**, T. Teranishi***, S. Kubono, S. Michimasa, H. Iwasaki, S.S.
- RIKEN
- K. Yamada, T. Gomi, N. Imai****, S. Takeuchi, H. Baba, S. Kanno, E. Takeshita, T. Minemura, Y. Yanagisawa, N. Aoi, Z. Elekes*****, M. Kurokawa, H. Sakurai, T. Motobayashi, M. Ishihara
- Rikkyo Univ.
- Y.U. Matsuyama, K. Kurita, K. Ieki
- Kyoto Univ.
- T. Murakami
- *Osaka U. **ANL, ***Kyushu U., ****KEK. *****ATOMKI

## Thank you very much

## Liquid Helium Target (CRYPTA)

- 100 - 250 mg/cm2
- 24-30 mm 7m Havar window
- Kept less than 4K sealed with Al cylinder
- Melting point of helium  is 4.2K @ 1atm
- Developed by CNS/Rikkyo/RIKEN

- Cold head

- Target

- H. Ryuto et al., NIMA 555 (2005) 1

## Typical Setup of Experimentinverse kinematics

**75**

**6**

- 120mg/cm2(4K)

**Charged particle detector**
**Plastic scintillator**
**ΔE, E, and position**

**12****Be**

**12****Be, ****13****B**

**Beam tracker**
**Position and direction**

- 30% Doppler Shift
-  @140°

**β****~****0.3**

**Gamma-ray detector**

**F3**

**vacuum**

**Separate high and low vacuum**

- H. Ryuto et al., NIMA 555 (2005) 1

## High Resolution
2.5 keV intrinsic resolution for 1.3 MeV 
High Sensitivity
 ~ 5 % for 1 MeV 
Position Sensitive
Resolution of Doppler Correction ~ 1 %

- 2.5 keV intrinsic resolution for 1.3 MeV 
- High Sensitivity
-  ~ 5 % for 1 MeV 
- Position Sensitive
- Resolution of Doppler Correction ~ 1 %

- CNS-GRAPE

**G**amma-**R**ay detector **A**rray with **P**osition and **E**nergy sensitivity

## 4He(12Be, 12Be ) at 60 A MeV

- 4He(12Be, 12Be ) at 60 A MeV

-  spectrum coincident with 12Be ejectiles
- 2.1 & 2.7 MeV States excited by (, ’)
- DWBA [ col. FF & folding pot.]

- Angular Distributions of 12Be*

- 2+

- 1-

## 4He(12Be, 12Be ) at 60 A MeV	Angular distribution of -decay after (,’) 

- 2.1 & 2.7 MeV States excited by (, ’)
- Alignments of 12Be* Anisotropic Angular Distribution of ****
- Consistent with Prediction of DWBA calculation assuming 2+ & 1- excitation, resp.
- Confirmation of 1- assignment for 2.7 MeV state

## Level Scheme of 12Be

- Level Scheme of 12Be

- B(E2; 0+2->2+1) = 7.0 (6) e2fm4
-                          = 0.87 (7) W.u.
- |< 0+2 |er2|0+1 >| = 0.87 (3) e fm2

## Performance of GRAPE

- 32Mg with ~0.26

- 2+→0+
- Doppler shifted

- 511 keV

- cos

- E(keV)

- 32Mg with ~0.26
- Doppler-shift corrected

- Position from pulse-shape analysis

## 4He(22O,23F) , 4He(23F,23F) , 4He(24F,23F)

-  ray spectra