Neutron%20Knockout%20from%20Intermediate%20Energy%20Beams%20of%2026,28Ne

1
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
2
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.

Z
28Ne
N
3
KNOCKOUT REACTION IN INVERSE KINEMATICS AT
ENERGIES OF 60-100 MeV/nucleon
E?
A
A-1
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

4
9Be(26Ne,25Ne)X
Elevel Jp l b ssp mb sobs mb C2Sobs C2Sth Eth
0 1/2 0 48(7) 41.7 46(7) 1.1(2) 1.347 0
1703 5/2 2 22(6) 21.5 21(6) 1.0(3) 2.346 1.779
3316 5/2 2 21(3) 19.3 20(3) 1.0(2) 1.837 2.971
J.R. Terry, J.L. Lecouey, Nucl. Phys. A734 (2004)
469-472
5
S800 Spectrograph
Segmented Germanium Detector Array SeGA
Focal Plane
Yellow arrow indicates beam path
6
9Be(28Ne,27Ne)X
Gamma-gamma analysis
765 keV gated
Inclusive 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
885 keV gated
119 keV
9Be(28Ne,27Ne)X
7
Momentum Distributions
765 keV
885 keV
l3
765 and 885 keV coincident events have momentum
distributions characteristic of an l2 neutron
removal
l2
l0
Longitudinal Momentum Distribution GeV/c
Events with no coincident transition gamma
Momentum distribution for events with no
coincident transition gamma ray is not consistent
with any single-l valued distribution. Combinatio
n of l0 and l3, 12 and 88, respectively, fits
the data.
l3
l3
l2
l0
Longitudinal Momentum Distribution GeV/c
8
Results
Jp l spartial mb ssp 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)
27Ne
9
Comparison to USD
5/2 2 1.08
3/2 2 0.10
5/2 2 0.04
Jp l C2S
Jp l C2S
(3,5)/2 2 1.36(9)
1/2 0 1.35
(3,5)/2 2 0.40(5)
7/2- 3 0.96(10)
3/2 2 1.58
(1/2) (0) 0.068(14)
USD
Exp
10
NILSSON DIAGRAM FOR N,Z lt 20
a - 0.5
a - 3.5
2
1
0
11
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)
12
Outlook

• Complete analysis of 28Ne
• Angular distributions of de-excitation gamma rays
• Analyze single-neutron removal from 30,32Mg

32Mg
30Mg
13
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