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Neutron Knockout from Intermediate Energy Beams of 26,28Ne

J.R. Terry1,2, D. Bazin1, B.A.Brown1,2, C.M. Campbell1,2, J.A. Church1,2, J.M. Cook1,2, A.D. Davies1,2, D.C. Dinca1,2, J. Enders1, A. Gade1, T.Glasmacher1,2, P.G. Hansen1,2, J.L. Lecouey1,W.F. Mueller1,H.

Olliver1,2, B.M. Sherrill1,2, J.A. Tostevin3, K. Yoneda1

1National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824, USA

2Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA

3School of Electronics and Physical Sciences, University of Surrey, Guildford GU2 7XH, UK

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Neutron Knockout from Intermediate Energy Beams of 26,28Ne

• Direct quantitative observation of negative parity intruder configuration in 28Ne.

• First observation of the level structure of 27Ne.

8 16

20

28

8

20

ZN

28Ne

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KNOCKOUT REACTION IN INVERSE KINEMATICS AT ENERGIES OF 60-100

MeV/nucleon

A A-1E

kA-1

Observables:

•Cross section of nucleon-removal reaction

•Population fraction to individual excited states by detection of coincident transition gamma rays

•Longitudinal momentum distribution of reaction residue

Three-body reaction theory based on Sudden and Eikonal approximations:

•Core-target and nucleon-target S-matrices calculated from Glauber theory

• Core-nucleon interaction modeled by a two-body Wood-Saxon potential

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9Be(26Ne,25Ne)X

J.R. Terry, J.L. Lecouey, Nucl. Phys. A734 (2004) 469-472

Elevel Jπ l b [%] σsp [mb] σobs [mb] C2Sobs C2Sth Eth

0 1/2+ 0 48(7) 41.7 46(7) 1.1(2) 1.347 01703 5/2+ 2 22(6) 21.5 21(6) 1.0(3) 2.346 1.7793316 5/2+ 2 21(3) 19.3 20(3) 1.0(2) 1.837 2.971

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S800 SpectrographSegmented Germanium Detector Array SeGA

Focal Plane

Yellow arrow indicates beam path

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9Be(28Ne,27Ne)XInclusive Cross Section: 66.7(33) mb

First observation of excited states in 27Ne: three gamma transitions: 119(3), 765(5), 885(5) keV.

37.7(20) % of events have no observed coincident transition gamma rays

Gamma-gamma analysis

885(5) 48.1(21)

765(5) 14.2(16)

0.83

0(17

) %0.

170(

17) %

E [keV] Branch [%]

119(

3) k

eV

0

119 keV

9Be(28Ne,27Ne)X

765 keV gated

885 keV gated

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l=0

l=3

l=2

l=3

l=0

l=2

l=3

765 keV 885 keV

Events with no coincident transition gamma

Momentum Distributions

765 and 885 keV coincident events have momentum distributions characteristic of an l=2 neutron removal

Momentum distribution for events with no coincident transition gamma ray is not consistent with any single-l valued distribution.

Combination of l=0 and l=3, 12% and 88%, respectively, fits the data.

Longitudinal Momentum Distribution [GeV/c]

Longitudinal Momentum Distribution [GeV/c]

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ResultsJπ l σpartial [mb] σsp [mb] C2Sobs

(3/2,5/2)+ 2 32.1(21) 23.6 1.36(9)

(3/2,5/2)+ 2 9.5(11) 23.6 0.40(5)

7/2- 3 22.1(21) 23(1) 0.96(10)

(1/2+) (0) 3.00(64) 44.4 0.068(14)

83.0

(17)

%

17.0

(17)

%

0.000

0.765(5)

0.885(5)

X

E [MeV]

27Ne

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Comparison to USD

1

0

2

3/2+ 2 1.58

1/2+ 0 1.35

5/2+ 2 0.04

3/2+ 2 0.105/2+ 2 1.08

Jπ l C2S Jπ l C2S

(1/2+) (0) 0.068(14)

7/2- 3 0.96(10)

(3,5)/2+ 2 0.40(5)(3,5)/2+ 2 1.36(9)

Sn=1.43 MeV

USD Exp

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0

NILSSON DIAGRAM FOR N,Z < 20 ½,

½0 ½)()1()1( K

I IaIIAEE

a = - 3.5

a = - 0.5

1

0

2

[200]1/2+1/2+

[202]3/2+3/2+

[330]1/2-3/2-

3/2+

5/2+

7/2-

1/2-

5/2-

5/2+

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1

Comparison of the (28Ne,27Ne) f7/2 Spectroscopic Factor with fp-shell occupancies from the Monte

Carlo Shell Modela)

a) Y. Utsuno, T. Otsuka, T. Mizusaki and M. Honma, Phys. Rev. C 60, 054315 (1999)

16 18 20 22 24N eutron N um ber

0

0.5

1

1.5

2

2.5<N

fp>

- Nno

rmal

Z = 10 (N e)

.

Exp. (N e)

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2

Outlook

• Complete analysis of 28NeAngular distributions of de-excitation gamma rays

• Analyze single-neutron removal from 30,32Mg

16 18 20 22 24N eutron N um ber

0

0.5

1

1.5

2

2.5

<Nfp

> - N

norm

al

Z = 10 (N e)

.

Z = 12 (M g)

Exp. (N e)

30Mg

32Mg

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3

Neutron Knockout from Intermediate Energy Beams of 26,28Ne

J.R. Terry1,2, D. Bazin1, B.A.Brown1,2, C.M. Campbell1,2, J.A. Church1,2, J.M. Cook1,2, A.D. Davies1,2, D.C. Dinca1,2, J. Enders1, A. Gade1, T.Glasmacher1,2, P.G. Hansen1,2, J.L. Lecouey1,W.F. Mueller1,H.

Olliver1,2, B.M. Sherrill1,2, J.A. Tostevin3, K. Yoneda1

1National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824, USA

2Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA

3School of Electronics and Physical Sciences, University of Surrey, Guildford GU2 7XH, UK