workshop lea colliga catania – 13 - 16 oct 2008

Workshop LEA COLLIGA Catania – 13 - 16 Oct 2008

N=50status

D. Verney /33

Position of the problem : why should we worry about N=50 ?1

Valence space above 78Ni ?2

Collectivity in the vicinity of 78Ni ?3

The N=50 shell closure and beyondStructure of nuclei “Northeast of 78Ni”

D. Verney, IPN Orsay


N=50status

D. Verney /33

N=50 : a bit of history

(d,3He)

-decay

« border » of the knowledge on nuclear structure

fission

(t,p)

Zendel et alInorg Nucl Chem 42, 1387 (1980)

Kratz et alNucl Phys A

250, 13 (1975)

Del Marmol et alNucl Phys A

194, 140 (1972)

Hoff -FogelbergNucl Phys A

368, 210 (1981)Ge83

Experimental status in year 2003

Sr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78Ni77Ni71 Ni72 Ni73 Ni74 Ni75 Ni76Ni70Ni69Ni68Ni67Ni66Ni65Ni64

Ge76Ge74Ge72

Y89

Zr90 Z=40

28

N=40 50

Cu65

Zn66 Zn67 Zn68 Zn70

Ga69 Ga71

Ge70 Ge73

As75

Se76Se74 Se77 Se78 Se80 Se82

Br79 Br81

Kr78 Kr80 Kr82 Kr83 Kr84

Rb85

Sr86 Sr87Sr84

Zr91

Se75 Se79 Se81 Se83

Kr85

Cu74

Zn75 Zn76 Zn77 Zn78

Ga79 Ga80fra

gmentation

Winger et alPhys Rev C

36, 758 (1987)

Beginning of -decay studies at PARRNe

OSIRIS /Studsvik

TRISTAN /Brookhaven

On

-lin

e m

as

s

se

pa

rati

on

Ch

imic

al

se

pa

rati

on

First structure data (’s) came from -decay (for N=50)1

Fission + ISOL technique

N=50 : present status

Sr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78Ni77Ni71 Ni72 Ni73 Ni74 Ni75 Ni76Ni70Ni69Ni68Ni67Ni66Ni65Ni64

Ge76Ge74Ge72

Y89

Zr90 Z=40

28

50

Cu65

Zn66 Zn67 Zn68 Zn70

Ga69 Ga71

Ge70 Ge73

As75

Se76Se74 Se77 Se78 Se80 Se82

Br79 Br81


Rb85

Sr86 Sr87Sr84

Zr91

Ge84Ge83


N=50status

D. Verney /33

isomeric decay: LISE-GANIL

radioactive beam: REX ISOLDECu75

Zn77 Zn78 Zn79

As84

Se85 Se86

-decay Orsay direct reaction in inverse kinematics :

Oak Ridge

DIC at Legnaro

ISOLDE laser

Experimental status in year 2008

-decay is still in the competition, good complementarities with DIC2

Fission + ISOL technique + post acceleration

BE(2)

Spectroscopic factors

DIC at Legnaro

Fusion-fission

Spontaneous fission

JYFLTRAP IGISOL

-decay Orsay

Why should we worry about N=50 ?

Historically from astrophysical considerations (and -decay experiments)

By Kratz et al. PRC 38 (1988)

Waiting point nucleus at N=50 80Zn

By Winger et al. PRC 36 (1987)

« »


N=50status

D. Verney /33

« it’s a joke » M. Bernas, private communication (2005)

1

d5/2

p1/2f5/2

g9/2

g7/2

s1/2

d3/2

h11/2

d5/2

g9/2

g7/2

s1/2

d3/2

h11/2

p1/2f5/2

50 40

70

40

70

N=3

N=4

N=5

HO

82

N>>ZN~Z

N~Z

Diffuse surface

N>>Z -

+

-From Dobaczewski et al. PRL72 (1994) 981.

Historically from structural considerations 2



N=50status

D. Verney /33


Because the N=28 shell effect is seen disappear in 42Si (see L. Gaudefroy’s Talk) 3B. Bastin et al., Phys. Rev. Lett. 99 (2007) 022503

First occurrence of the vanishing of shell effect originating from spin orbit

Probably due to tensor force in the residual interaction via an Otsuka-like mechanism

The same tragic destiny is predicted for Z=28T. Otsuka et al. PRL95, 232502 (2005)


N=50status

D. Verney /33

E (MeV)

-14,386

-13,233

-11,831

-7,121

40

f5/2

p3/2

p1/2

g9/2

Proton single particles

From Ji et Wildenthal Phys. Rev. C 38, 2849

(1988)


N=50status

D. Verney /33

Is 78Ni doubly magic ? Persistence of Z=28 and N=50

How fast those collectivity sets in?What is the nature of valence space which opens up just above ?


At the beginning of the PARRNe project at IPN (very end of the 90’s)4

Sr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78Ni77Ni71 Ni72 Ni73 Ni74 Ni75 Ni76Ni70

Ge76Ge74

Y89

Zr90

50

As75

Se76 Se77 Se78 Se80 Se82

Br79 Br81


Rb85

Sr86 Sr87Sr84

Zr91

Se79 Se81 Se83

Kr85

Cu74

Zn75 Zn76 Zn77 Zn78

Ga79 Ga80


From Ji et Wildenthal Phys. Rev. C 38, 2849

(1988)

d5/2 d3/2s1/2gZ/2

Neutron single particles

Zr93Zr92 Zr92 Zr93 Zr94 Zr95

f5/2

p3/2

p1/2

g9/2

Zr96

Known part of t

he

valence sp

ace

Unknown part of t

he

valence sp

ace

OK

OK

??

?

-Residual

interaction

1236(9/2-)


N=50status

D. Verney /33

Single particle ordering close to 78Ni Protons : odd-N=50 isotones

hot subject ! -decay experiment redone at ISOLDE and Oak Ridge

(same lines as us)

observed in -decay at Orsay (PARRNe)D. Verney et al PRC 76 (2007)

054312

observed in DIC experiments at

LegnaroG. De Angelis et al. NPA 787

(2007) 74c

unchallenged! nor by spontaneous fission nor by fusion-

fission data

Zn81

Sr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78

Y89

Zr90

50

Zr91 Zr93Zr92 Zr92 Zr93 Zr94 Zr95 Zr96

Se85 Se86

As84

Ge83 Ge84

3 protons out of a 78Ni core

PARRNe

Exp

A.F. Lisetskiy et a

l.,

PRC 70 (2004)

JW modifie

d,

PRC 76 054312(2007)

Ji & Wildenthal,

PRC 40, 389 (1989)

BA Brown (jj4b)

Private communication

= 2p3/2 qp state



N=50status

D. Verney /33

Sr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78

Y89

Zr90

50


Se85 Se86

As84

Ge83 Ge84


2p3/2

1f5/2

81Ga Z=31 N=50

2p3/2

1f5/2

83As Z=33 N=50



N=50status

D. Verney /33

Sr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78

Y89

Zr90

50


Se85 Se86

As84

Ge83 Ge84


E (MeV)

40

f5/2

p3/2

p1/2

g9/2

Proton SPE ordering in a 78Ni mean field

351.1 keV

0 keV

802.8 keV

Experiment

351.

1 ke

V45

1.7

keV

0

200

400

600

800

1000

1200

1400

1600

1800

keV 81Ga Z=31 N=50

f5/22

p3/2

J=3/2

f5/23

J=5/2, v=1

J=3/2, v=3

To be definitely validated in (d,p) reaction (Oak Ridge ? REX ISOLDE ? SPIRAL2 ?)

f5/23

Ga84

247.81/2+observed in

2H(82Ge,p)83Ge at Oak Ridge

Thomas et al. PRC 71 (2005) p. 021302

observed in -decay at PARRNe

O. Perru et al.EPJ A 28 (2006) 307

Single particle ordering close to 78Ni Neutrons : odd-N=51 isotones


N=50status

D. Verney /33

Ga83

Sr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78

Y89

Zr90

50


Se85 Se86

As84

Ge83 Ge84

4 protons + 1 neutron out of a 78Ni core

observed in n-decay at ALTO

M. Lebois article in preparation

2d5/2

3s1/2

(3/2,5/2+)

7/2+



N=50status

D. Verney /33

Core – particle (weak) coupling model

Zn81

Sr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78

Y89

Zr90

50

Zr91

Se85

Ge83

Kr87

Sr89

Even-even semi-magic core

L. S. Kisslinger & R. A. Sorensen Rev. Mod. Phys., 35, 853, (1963)

Thankappan & TruePhys. Rev. B, 137, 793 (1965)

Neutron single particle

Core excitation energies taken from experiment : E(2+), E(4+), E(0+2) etc

Parameters :

Q>0Q=0 Q<0

Vector space :0+1 2d5/22+1 2d5/22+1 3s1/2Etc…



N=50status

D. Verney /33

M. Lebois, Thesis Univ. Paris-Sud XI (Sept 2008)

Sr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78

Y89

Zr90

50

Zr91

Sr89

Thomas et al. PRC 71 (2005) p. 021302



N=50status

D. Verney /33

2d5/2

3s1/2



N=50status

D. Verney /33

Sr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78

Y89

Zr90

50

Zr91

Ge83




N=50status

D. Verney /33

N=58 ?



N=50status

D. Verney /33


Sr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78

Y89

Zr90

50

Zr91

Zn81



N=50status

D. Verney /33

d5/2

d3/2

s1/2

gZ/2


Proton SPE ordering in a 78Ni mean field

351.1 keV

0 keV

802.8 keV

1621.6 keV

351.

1 ke

V45

1.7

keV

0

200

400

600

800

1000

1200

1400

1600

1800

keV

1236 keV

(5/2-)

(3/2-)

(3/2-)

(9/2-)

As83

Ge82

Ga81

Zn80

Cu79

Ni78

+1p

+3p

+5p

Ge83

81Zn

2d5/2

3s1/2?

Fed in -decay

Low spins only

Sr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78

Y89

Zr90

50


Se85 Se86

As84

Ge83 Ge84

Zn80

How fast those collectivity sets in?

Sr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78Ni77Ni71 Ni72 Ni73 Ni74 Ni75 Ni76Ni70

Ge76Ge74

Y89

Zr90

50

As75

Se76 Se77 Se78 Se80 Se82

Br79 Br81


Rb85

Sr86 Sr87Sr84

Zr91

Se79 Se81 Se83

Kr85


d5/2 d3/2s1/2 gZ/2


Zr93Zr92 Zr92 Zr93 Zr94 Zr95

f5/2

p3/2

p1/2

g9/2

Zr96

Known valence sp

ace

Unknown valence

space

OK

OK

?

-Residual

interaction

Single particle ordering close to 78Ni


N=50status

D. Verney /33

Collectivity close to 78Ni


N=50status

D. Verney /33

Ga85Ga84

Sr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78

Y89

Zr90

50


Se85 Se86

As84

Ge83 Ge84

4 protons + 2 neutrons out of a 78Ni core

-decay ALTO+ ISOLDE and Oak Ridge

See contribution by F. Ibrahim Wednesday

(0¯)

(4¯)

1/2+

52

24

7.8

5/2+

n

Even-even nuclei

Collectivity close to 78Ni Z=32 even-even nuclei


N=50status

D. Verney /33

Collectivity close to 78Ni N=52 even-even nucleiN=42 N=44

N=46 N=48

N=50 N=52

O Perru thesis Paris-Sud XI (2004) & J. Libert private communication

HFB calculation using the Gogny interactionGCM Bohr dynamics

0.1 0.2 0.3 0.40 0.1 0.2 0.3 0.40

0.1 0.2 0.3 0.40 0.1 0.2 0.3 0.40

0.1 0.2 0.3 0.40 0.1 0.2 0.3 0.4041

+ exp

41

+ hfb

21

+ exp

21

+ th

N=50

N=54

0.1 0.2 0.3 0.40

HFB calculations

triaxial static shape predicted !


N=50status

D. Verney /33

Strong increase of collectivity

Collectivity close to 78Ni N=52 even-even nuclei


N=50status

D. Verney /33

Exp

ect

ed Z

=2

8 s

hell

closu

re

Z+

40 s

ubsh

ell

eff

ect

Ge : a special case ?


N=50status

D. Verney /33



N=50status

D. Verney /33

Local minimum at Z=32



N=50status

D. Verney /33

Local minimum, not at mid distance Z=28-40 !

REX-ISOLDE

J. Van de Walle et al.PRL 99, 142501 (2007)

80Zn 82Ge84Se

86Kr

88Sr

90Zr

A Prévost et al. EPJ A 22 (2004) 391Medium/high spin states obtained from fusion/fission at the Vivitron (Euroball IV)

-

f7/2

p3/2

p1/2

f5/2

g9/2

28

50

40

f7/2

p1/2

g9/2

d5/2

p3/2f5/2

protons neutrons

-

+

+ +



N=50status

D. Verney /33

A first explanation for the observed downsloping of the p-h states

Y.H. Zhang et al. PRC 70 (2004) 024301Medium/high spin states fed in DIC at Legnaro (GASP)

84Se

SM calculation proton valence space

SM calculation proton valence space + neutron 1phf7/2

p3/2

p1/2

f5/2

g9/2

28

p1/2

g9/2

d5/2

protons neutrons

504 MeV

The gap used in the calculation has the good size



N=50status

D. Verney /33

Collectivity close to 78Ni Even-even nuclei

Sr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78

Y89

Zr90

50


Se85 Se86

As84

Ge83 Ge84

REX ISOLDE J. Van de Walle et al.PRL 99, 142501 (2007)

“The results for N=50 isotones indicate a good N=50 shell closure and a strong Z=28 proton core polarization.”


N=50status

D. Verney /33

1492 keV

O Perru thesis Paris-Sud XI (2004) & J. Libert private communication

HFB calculation using the Gogny interactionGCM Bohr dynamicsSr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78

Y89

Zr90

50


Se85 Se86

As84

Ge83 Ge84



N=50status

D. Verney /33


Sr88

Rb87

Kr86

Br85

Se84

As83

Ge82

Ga81

Zn80

Cu79

Ni78

Y89

Zr90

50


Se85 Se86

As84

Ge83 Ge84


N=50status

D. Verney /33

80Zn78Zn

76Zn74Zn72Zn

66Zn 68Zn 70Zn

Potentials Zn


N=50status

D. Verney /33

Conclusions

A new single particle ordering appears close to 78Ni1

N=50 offers nothing but a local parenthesis of rigidity2

The underlying microscopic mechanism remains to be understood

3


d5/2

d3/2

s1/2

gZ/2


f5/2

p3/2

p1/2

g9/2

Local minimum of the N=50 shell gap for Z=32 seems to have considerable influence on structureCollectivity sets in very rapidly just below and just above N=50

From the shell model point of view : description is alright up to N=50, beyond N=50 much work to do. Is 78Ni a good core ?Bohr dynamics very efficient….


N=50status

D. Verney /33

Thank you !

workshop lea colliga catania – 13 - 16 oct 2008

Documents

bdecay experiments

decay studies

verney et

beginning of b

kratz et alnucl phys

hebdecay border

marmol et alnucl phys

valence space unknown