Spectroscopy of 9Li : the new N=6 closed shell nucleus

Rituparna Kanungo

St. Mary’s University, Canada

A.N. Andreyev, L. Buchmann, B. Davids, G. Hackmann, D. Howell, P. Khalili, B. Mills, E. Padilla Rodal, S. Pieper, J. Pearson, C. Ruiz, G. Ruprecht,

A. Shotter, I. Tanihata, C. Vockenhuber, P. Walden, R.B. Wiringa

Simon Fraser University, Canada

Argonne National Laboratory, USA

TRIUMF, Canada

New shell closures in neutron-rich nuclei

N=6

N=16

N=30

N

Z

10 20 30

10

20

Z=16

N=32

break in Qβ−

break in Sn

break in Eex1st

break in Spdisappearance

of usual magicnumber

5

15

5 2515

Z=16

N=16

N=6

R. Kanungo et al, PLB 528 (2002) 58

Search for N=6 shell closure through spectroscopy of 9Li

Structure of 9Li

8Li

n

€

ψgs9Li( ) = ψ i

i, j

∑ 8Li( ) ⋅ψ j n( )

States of 8Li Orbitals of neutron

s1/2

p3/2

p1/26

8Li-levels

2+

1+0.98

0.0

2.25

3.21

3+

1+

8Li

s1/2

p3/2

p1/26

9Lineutrons in

8Li

[if N=6 is not closed shell] [predominant configuration if N=6 is closed shell]

d(9Li,t)8Li @ ISAC, TRIUMF

LEDA LEDA

S2

target(CD2)n

S2[DSSD]

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

@ TUDA

E=1.68A MeV

t

8Li

9Li

E = 0.5%LEDA = 1.1o - 2.1o

S2 ~ 0.2o beam ~ 5mradbeam ~ 1mm

r=5mm

r=0.5mm

d(9Li,t)8Li : S2 only

8Ligs

6000

9000

12000

15000

8Liex1

Elastic

scattering

6 8 10 14 16

(a)

Laboratory Angle [deg]

C- elasticd- elastic

Beam Intensity : Rutherford scattering with COptical potentials : ‘d’ -elastic scattering

Q- resolution ~ 100keV()ISAC1 = 0.3 mm mrad/β

0

200

400

600

800

1000

1200

1400

1600

1800

0.5 1 1.5 2 2.5 3 3.5Q-value [MeV]

8Liex1(1+)

8Ligs

6000

9000

12000

15000

Ene

rgy

[ke

V]

0

500

1000

1500

2000

2500

3000

0.5 1 1.5 2 2.5 3Q- value [MeV]

d(9Li,t)8Li : LEDA only

8Liex1(1+) 8Ligs

Simulation

Data

8000

26 28 30 32 34 36 38 40 42 44 46 48

8Ligs

8Liex1

4000

12000

Ene

rgy

[ke

V]

lab [deg]

elastic

8Liex2

elastic

8Liex3

d(9Li,t)8Li : S2 and LEDA coincidence

Simulation

Data

0

200

400

600

800

1000

1200

1400

1600

1800

2000

-2 -1.5 -1 -0.5 0 0.5 1 1.5Q-value [MeV]

8Liex2(3+)

2000

4000

6000

8000

Ene

rgy

[ke

V]

26 30 34 38 42 46 50lab [deg]

elastic

8Liex3

Angular distribution and DWBA calculation

PRELIMIN

ARY

8Ligs (2+) 8Liex1(1+)

8Liex2(3+)

20 40 60 80 100 120

cm [deg]100

100

10

1

d/d

[m

b/sr

]

Spectroscopic factors : 9Li

Total occupation probability of p3/2 orbital ~ 3.5

Consistent with N=6 shell closure

€

S 8Li

exp =

dσ

dΩ

⎛

⎝ ⎜

⎞

⎠ ⎟exp

dσ

dΩ

⎛

⎝ ⎜

⎞

⎠ ⎟DWBA

⋅St

valence neutrons mainly occupy p3/2 orbital

St = 1.5 [Ref. Satchler used]

VMC calculations yield St = 1.3.

PRELIMIN

ARY

Summary

Ground state structure of 9Li is investigated through d(9Li,t)8Li one neutron transfer

The majority of valence neutrons occupy the p3/2 orbital.

Consistent with N=6 shell closure.

The spectroscopic factors are in fair agreement with theoreticalestimates.

Acknowledgements

Our thanks to:

ISAC beam delivery team

Thank you for your kind attention

Prof. J.P. Schiffer, ANL for helpful discussions

University of York for the LEDA array

Prof. P.Kunz, Colorado for helpful discussions

Prof. T. Davinson, Edinburgh for helpful discussions