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University of Brighton
Isospin purity in the A=38, T=1 nuclei tested via lifetime
measurements in 38K.F. M. Prados Estevez, A.M.Bruce, M.J.Taylor1
University of Brighton
H.Amro, C.W.Beausang2, R.F.Casten, J.J.Ressler3
Yale University
C.J.Barton1
Daresbury Laboratory
C.Chandler, G.Hammond1
University of Keele
Current address: 1 University of York 2: University of Richmond 3: Simon Fraser University
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University of Brighton
Systematics of B(E2) values and matrix elements between 2+ (T=1) and 0+ (T=1) states in T=1
isospin triplets.
0+ (T=1)
2+1(T=1)
2+2(T=1)
A=22: Ne, Na, Mg
A=26: Mg, Al, Si
A=30: Si, P, S
A=34: S, Cl, Ar
A=38: Ar, K, Ca
A=42: Ca, Sc, Ti
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University of Brighton
Systematics of N=Z=odd nuclei
2+1 -> 0+
2+2 -> 0+
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University of Brighton
Is it the right 2+ state?
The energy agrees with the neighbours.
2+ T=1
1+ T=0
38K
38Ca
1+ T=0
0+ T=1
3+ T=0
2206 keV 2167 keV 2403 keV
38Ar
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University of Brighton
Comparison across the T=1 triplet
2 * M (Tz=0)
M (Tz=1) + M(Tz=-1)
Data suggests all three values are low but, in fact, it’s hiding something:
(for Tz=0 nucleus)
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University of Brighton
The variation of M against Tz Tz defined as (N-Z)/2
38K
38Ca38Ar
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University of Brighton
Clearly something of interest in 38K:
7+ T=0 22s
2+ T=1
1+ T=0
1+ T=0
0+ T=1
3+ T=0 38K
Fusion-evap not possible:
3 previous measurements
40Ca(d,) 76 (50) fs
39K (3He,) 54 (25) fs
40Ca(d,) 90 (25) fs
Weighted average = 72 (16) fs
2403 keV
2272 keV 1944 keV
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University of Brighton
Experimentalset-up.
Target:220 g/cm2 Ca on aNi backing of 1mg/cm2 . Flash of gold on front face.
d
-particles
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University of Brighton
Experimental set up, 8 solar cells ~ 2cm from the target.Angles subtended 1430-1660.
8 clovers (900, 1400) and 2 LEPS (900).
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University of Brighton
Angular behaviour of the 1944 keV transition.
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University of Brighton
F() value from the 1944 keV transition 0.868 (36)
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University of Brighton
Data fitted with a modified version of Dechist.
114 (26) fs
159 (30) fs
Fitted values for the 2403 keV level:
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University of Brighton
The variation of M against Tz Provisional data point added for 38K
38Ca38Ar
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University of Brighton
Branching ratio of the 2+ state is also important:
1+ T=0
0+ T=1
3+ T=0
2+ T=1
1+ T=0
38K
2403 keV
2272 keV 1944 keV
Ratio from previous work is:
2272 keV: 6.41944 keV: 100
but 1944 is clearly a doublet which we are currently trying tosort out, this will increase the relative strength of the 2272 keV transition. A factor of 2 would take the matrix element to 7.5.
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University of Brighton
Shell model calculations
0
5
10
15
20
-1.5 -0.5 0.5 1.5
Tz=(N-Z)/2
M (
efm
^2)
22
26
30
34
38
B.A.Brown et al
Phys Rev C26(1982)2247
sd model space
Chung-Wildenthal
wave functions
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University of Brighton
Thanks to all Yale staff for their efforts during the experiment.
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University of Brighton
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University of Brighton
Dedication
Dave Warner1950-2005