Spectroscopy of exotic nuclei

Reiner Krücken

Physik Department E12Technische Universität München

Maier-Leibnitz Laboratory of TU München and LMU Münchenfor Nuclear-, Particle-, and Accelerator Physics

From QCD to atomic nuclei

u ud

Quarks,

Gluons

nucleon-nucleoninteraction

(ab-initio Models)

Light nuclei

(A10)?

QCD

Protons,

Neutrons

Ab-initio calculations of light nuclei

7500 CPU hours

From QCD to atomic nuclei

u ud

Quarks,

Gluons

nucleon-nucleoninteraction

(ab-initio Models)

Light nuclei

(A10)

?

?

Heavy nuclei

effectivenucleon-nucleon

interaction

(Mean-field theories)

QCD

Protons,

Neutrons

Shell structure in nuclei and metal clusters

Annu. Rev. Nucl. Part. Sci. 2001 , Vol. 51: 219-259. H.O. + L2 +

L•S

2

8

20

28

50

82

126

184198

138

92

58

40

20

8

2

20

8

2

112

70

40

168

S.G. Frauendorf, C. Guet

Central Questions in Nuclear Structure Physics

• Where are the limits of nuclear stability?• How does shell structure change far from stability?• What are the phases, relevant degrees of freedom, and symmetries of the nuclear many-body system?• Are there new modes of collective excitation?

• How are the Heavy Elements produced? Unified theoretical framework

with predictive power

Diversified experimental strategy to understand the Structure and Dynamics of Exotic Nuclei:

Measure Ground State Properties Gamma-ray spectroscopy of excited

states Reaction studies

r-process and shell structure

Nuclear shell structure- Defines r-process path- Imprinted in abundance pattern- maybe modified for exotic nuclei

- Fission may fill the holes- Depends on shell structure

r - process

G. Martinez-Pinedo et al.

Pfeiffer et al.

40 50 60 70 80 90-2

-1

0

1

element number

abun

danc

e lo

g(X

/H)-

12

CS22892-052 (Sneden et al. 2003)

solar r

Production of radioactive ion beams

Production of radioactive ion beams

Isotope Separation On-Line

Diffusion from thick target- depends on

chemistry- Needs time

Fragments move with beam velocity (30-90% c)

Reaction induced by light projectile (p,d,n) in thick target

Exotic nuclei are produced in thin target as fragment of heavy beam

In-flight separation

In-flight production of radioactive beams

Projectile fragmentation or fission at high energies (50 -1000 AMeV)

Both fragments are highly excited ad evaporate

nucleons

Fig. by T. Glasmacher (NSCL/MSU)

Br - DE - Br Separation Method

UNILAC

SIS

FRS

ESR

100 m

Fragment Identification

DE

DE

TOF

FAIR: Facility for Antiproton and Ion Research

Primary Beams

• 1012/s; 1.5-2 GeV/u; 238U28+

• Factor 100-1000 over present in intensity

Secondary Beams

• Broad range of radioactive beams

up to 1.5 - 2 GeV/u; • up to factor 10 000 in intensity over present

• Antiprotons 3 - 30 GeV

Storage and Cooler Rings

•Radioactive beams

•e- - A and Antiproton-A collider

100 m

UNILAC SIS 18

SIS 100/300

HESR SuperFRS

NESR

CRRESR

GSI todayGSI today

Future FacilityFuture Facility

ESR

1.4 GeV

ISOLDE at CERN

from PS Booster

REX-ISOLDE

Modifications of nuclear shell structure

Two-neutron separation energies

Fig. by R.F. Casten

Shellclosure

The extreme single-particle model

StrongSpin-orbitFrom individual nuclei with NN interaction

to mean field with residual interaction

N=82

Probing shell closures: Decay Spectroscopy

A. Jungclaus et al., PRL 99, 132501 (2007)

I. Dillmann, PRL91 (2003) 162503

b-decay Q-value (ISOLDE): 130Cd less bound Quenching of N=82 shell ?

no shell quenching information on excited states essential!!

SIMBA Implantation Detector in RISING

Ch. Hinke, K. Eppinger, K. Steiger

Shell modification through softer potential

T.R. Werner, J. Dobaczewski, W. Nazarewicz, Z. Phys. A358 (1997) 169

Possible signatures: new shell gaps (e.g. N=70 in 110Zr) reduction of spin-orbit splitting in neutron-rich nuclei increased neutron skin

Pfeiffer et al.

zentralLS Vdr

dV

Shell modification through residual interaction

O. Sorlin, M.G. Porquet,Prog. Part. Nucl. Phys. 2008

24O doubly magic

32Mg deformed

Effective single particle energies

T. Otsuka et al.

N=20

Z=8

... what is the heaviest bound oxygen isotope????

unboundbound

Non-existence of 28O (Z=8,N=20)H. Sakurai et al., Physics Letters B 448 (1999) 180RIPS@RIKEN

Position x-y è trajectory B r è p, A/ZTOF è v è AdE/dx è Z

The neutron drip-line

Otsuka et al., arXiv:0908.2607v1 [nucl-th]

O F: 1 extra proton can bind 6 more neutrons

Is 24O doubly magic?

24O knock-out experiment at the GSI FRS

48Ca 1A GeV

carbon4.05 g/cm2

FRSoperation in 'dispersion matched mode'

→ direct momentum measurement at S4

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

6.347 g/cm2 Be

Excellent agreement with predictions for N=16 shell closure

1h11/2 neutrons

1h11/2 protons

1g7/2 protons

11/2-

7/2+

Reduced spin-orbit or tensor force?

T. Otsuka et al., PRL 97 (2006) 162501

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

j<

j>

j’>

j’<

protons

neutrons

J.P. Schiffer et al., PRL 92 (2004)

Z=51 Sb isotopes

FRIB

Intermediate energy Coulomb excitation

Au

Au

40S

Doppler-correction

20-50 MeV/u

Possible complications:a) Need to separate EM interaction from nuclear interactionselect small scattering angles large distance between nuclei

b) Possible feeding from higher lying 2+ states

T. Glasmacher, Annu. Rev. Nucl. Part. Sci. 1998.48:1-31

Collectivity of 32,34Mg

32Mg: E(4+)/E(2+) = 2.6

34Mg: E(4+)/E(2+) = 3.2

Rotor: E(4+)/E(2+) = 10/3

Ar S Si Mg Ne 38 36 34 32 30

100

50

0

150N=20

B(E

2;

2+

0

+)

[e2fm

4]

Without N=20 shell

With N=20 shell

T. Motobayashi et al. Phys. Lett. B 346 (1995) 9.

Secondary fragmentation of 36Si beam

K. Yoneda et al., Phys. Lett. B 499 (2001) 233

Transfer reactions

• (d,p), (3He,d): Stripping of neutron or proton from light ion

• (p,d), (3He,a): Pick-up of neutron/proton by light ion

• Exampled + 90Zr p + 91Zr or 90Zr (d,p) 91Zr

Other examples:(d,p), (a,3He)…(p,d), (3He, a)…(3He, d), (a, t)…(d,3he), (t,a)…

Example – 54Fe(d,p)55Fe

Energy (keV)

counts

5 keV FWHM

25 MeV

deuterons

55Fe

DWBAd

dS

d

d

exp

MunichQ3D

Transfer set-up T-REX inside MINIBALL

V. Bildstein, K. Wimmer

T-REX position sensitive silicon detector array:• forward barrel (DE-E): 140/1000 μm

• backward barrel/CD: 500 μm silicon• 3◦ − 5◦ angular resolution• energy resolution of 60 keV (backward) to 2

MeV (forward) at 3 MeV/u

efficiency of full 4p array: 62%

40

39

41

323130

29

282726

25

2423

18 O

F

Ne

24

40

383736

363534

33

54

46

44

43

42

40

48

50

45

49

48

47

46

32

Na

Mg

Al

Si

P

S

Cl

Ar

K

Ca

Sc

Ti

36

43

44

19

31

22

21

20

34

47

51

classic shell closures

Predictednew shell closures

Modification of shell structure

Island of inversion

deformed g.s.

Giant resonances

probe bulk properties of nuclei symmetry energy compressibility effective NN interaction

Radioactive beams allow tostudy isospin dependenceof nuclear bulk properties

New Phenomenon: Soft Modes

Dipole Excitations of Neutron-Rich Nuclei

neutron skin core vibration

LAND collaboration A. Klimkiewicz, PRCL subm. P. Adrich, PRL 95 (2005)

124Sn

132Sn

Photoabsorption

Coulomb excitation

130Sn

P. Ring et al.

Symmetry Energy, EOS and Neutron Stars Pygm

y

stre

ngth

N. Paar

RQRPA

Symmetry energy

Expansion of energy per nucleon around saturation density 0

a4 = Symmetry energy in neutron matter(asymmetry parameter)