Proton resonance elastic scattering of 30Mg
for single particle structure of 31Mg
N. Imai (KEK)
Single particle energies
at ‘Island of inversion’
• Energy gap between pf-sd orbits.
• Single particle states will be a
direct evidence of the shell
evolution.
T. Otsuka et al, PRL104,012501
Spherical vs. deformed
• g.s. of 31Mg is well deformed.
m(31Mg g.s.) = -0.88355(15)mn
Ip = 1/2+ G. Neyens, PRL94, 022501
• Ip = 7/2- state should be in high
Ex in the deformed potential.
I. Hamamoto, PRC76, 054319
• Low-lying 7/2- state should be
spherical.

7 / 2  Mg(0 )  7 / 2 30 Mg(2 )  3 / 2
30
How much is S of 7/2-?
Isobaric Analog Resonances of
bound states of 31Mg
p
n
Parent state
p
n
IAS
fcorefn fn = fp fcorefp
Resonance shape
= angular momentum (l)
Resonance width
= total width (Gtot)
Resonance height
= proton width (Gp) ~ Spp
Thick target inverse kinematics(T2IK)
proton resonance elastic scattering with RIBs
Excitation function of ds/dW(qlab.~0)
cf.) V.Z. Goldberg, ENAM98
1. One fixed energy
2. Large cross section
~ several 10 mb/sr
3. High-energy recoil proton
~ 4x Ereso
30Mg
3MeV/u
Easy identification of resonances
Recoil proton
Thick hydrogen
Target (CH2)
Example: p(34Si,p) for 35Si@RIKEN
34Si:
4-6 MeV/u
7x104 pps
1 days accumulation
CH2
C
S of f(7/2-) in 35Si was successfully determined.
N. Imai et al., in preparation.
Expected excitation function of p(30Mg, p)
#
Ex
(keV)
Jp
Ecm
(MeV)
Gp
(keV)
1
0.
1/2+
2.307
57.
2
50.
(3/2+)
2.357
11.
3
221.
(3/2-)
2.528
50.
4
461.
(7/2-)
2.768
6.
5
673.
(3/2+)
2.980
27.
6
945.
(5/2+)
3.252
27.
S=0.3 was assumed.
30Mg7+
@2.83MeV/u beams
(Ecm < 2.76 MeV)
Experimental setup
Vacuum chamber for IS512
•Target: 60 mm (~ 6mg/cm2) thick CH2 target
6 mg/cm2
C target
•Detector: dE-E annular (0.3+ 0.5 + 0.5 mm)
or square type (0.3+ 1.0 mm)
cf.) Highest Ep is 12 MeV  1 mm thick SSDs
•Absolute s: off-resonance cross sections
dEp < 80 keV for qlab< 5.5 deg
Contamination in beam
Ex. 30Mg7+: 82%, 30Al7+ :18%
O.T. Niedermaier, PhD thesis.
Assuming 30Mg7+ (A/q=4.2857): 80%
30Al7+
:20%
Red line: inclusive measurement
20% 30Al + 80% 30Mg (p,p)
Black line: 100% 30Mg(p,p)
Blue line: 20% 30Al(p,p)
Even with the inclusive measurement, shape
does not change so much.
Some times, laser-off measurement will be
needed for contribution of 30Al beam.
Yield Estimation
•
•
•
•
ds/dW ~ 80 mb/srlab. (off-resonance)
d = 160 mg/cm2
(20 keV/u-loss of 30Mg in CH2)
I = 4x104 pps
DS = 29 msr
( qlab < 5.5 deg)
100 counts/day/20keVcm-bin
Beam time request
Beam transports
3 shifts
IAR measurements w/ stable
26Mg beams including circuit
tuning
2 shifts
IAR measurements w/CH2
w/30Mg
3 shifts
BG runs w/C target w/30Mg
2 shifts
total
10 shifts
Collaboration
• KEK :
N.I., Y. Hirayama, H. Ishiyama, S.C. Jeong,
H. Miyatake, Y.X. Watanabe
• Lund: J. Cederkall
• Kyusyu-U: T. Teranishi
• CNS, Univ. o Tokyo: H. Yamaguchi, S. Kubono
• Fin
(d,p) vs Isobaric Analog Resonance
• (d,p) reaction
Direct measurement
wide angular distribution of ds/dW
ds/dW @ forward angle
dElab. ~ 1/3 dEc.m.
g-ray : suffer from decay scheme
• (p,p) resonance scattering
Indirect measurement
excitation function of ds/dW
ds/dW @ backward angle~180 degc.m.
dElab. ~ 4 dEc.m.
Lower isospin excitation sometimes problem
30Mg(d,p)31Mg*
(460 keV)
DWUCK4
DL=3, S=1
DL=2, S=0.4
Effect of T< excitation
26Mg(p,p)
for IARs of 27Mg
0.4 keV resolution
6 resonances
C.R. Westerfeldt et al,
NPA303(‘78)111
20 keV resolution
Fit with 2 resonances
(l=1, and 0)
#
Gp
(keV)
E(keV)
Jp
Gpfit
Gtfit
Efit(keV)
1
40.9
2022.2
3/2-
50.2(43)
57.1(23)
2015(2)
2
0.130
2047.9
3/2+
-
-
-
3
70.4
2049.2
1/2+
66.4(33)
66.4(162)
2051(3)
4
0.075
2049.3
7/2-
-
-
-
5
1.1
2140.4
3/2+
-
-
-
6
5.6
2141.8
1/2-
-
-
-
Estimation of Gp
• R-matrix theory
 S pp Pl e 2d  2u n2 (r ) 
Gp  

 ( N  Z  1) mr  r  ac
2008/2/19
3rd RIBF-PAC
•
30Mg(2+):
Ex. 1482 keV