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Particle hole states in 42Ca excited by the 41K(3He, d)42Ca reaction
Volume 27B, number 5
PHYSICS
PARTICLE BY THE
LETTERS
5 August 1968
HOLE STATES IN 42Ca EXCITED 41K(3He, d)42Ca REACTION*
J. S. F O R S T E R , K. B E A R P A R K , J. L. H U T T O N and J. F. S H A R P E Y - S C H A F E R
Chadwick Laboratory, University of Liverpool, UK Received 20 June 1968
P a r t i c l e hole states in 42Ca up to an excitation energy of 5.79 MeV have been determined. The quartet of states arising from the (ld~ -1, lf~) configuration has been identified and from the extracted spectroscopic factors spin assignments of 4- and 2- are made to the 3.95 MeV and 4.50 MeV levels.
T h e 41K(3He, d)42Ca r e a c t i o n h a s b e e n u s e d to i n v e s t i g a t e p a r t i c l e - h o l e s t a t e s in 4 2 C a f o r m e d b y c o u p l i n g a ld~ p r o t o n h o l e to a p r o t o n in t h e lf~ o r 2p s h e l l s ; t h e g r o u n d s t a t e of 41K i s e x p e c t e d to be m a i n l y a c l o s e d s - d s h e l l c o r e p l u s a l d ~ p r o t o n h o l e and two lf½ n e u t r o n s . T h e s t a t e s f o r m e d can b e T = 1 o r 2 s t a t e s ; the T = 2 s t a t e s a r e t h e a n a l o g u e s of s t a t e s in 42K and a r e e x p e c t e d to s t a r t at an e x c i t a t i o n e n e r g y of about 7.6 MeV in 42Ca. T h e e x p e r i m e n t w a s c a r r i e d out w i t h t h e 11.0 MeV 3He++ b e a m f r o m t h e L i v e r p o o l U n i v e r s i t y t a n d e m V a n de G r a a f f a c c e l e r a t o r . T h e r e a c t i o n d e u t e r o n s w e r e o b s e r v e d in a s u r f a c e barrier detector telescope with pulse multiplic a t i o n p a r t i c l e i d e n t i f i c a t i o n t e c h n i q u e s [1]. T h e t a r g e t s , e n r i c h e d to 95.35% in 41K, w e r e p r e p a r e d by e v a p o r a t i n g 2 0 0 ~ g / c m 2 of KI onto a thin c a r b o n b a c k i n g . T h e e r r o r in t h e e x p e r i m e n t a l a b s o l u t e c r o s s s e c t i o n s i s e s t i m a t e d to b e + 20%. T h e l e v e l s c h e m e of 4 2 C a h a s r e c e n t l y b e e n d e t e r m i n e d f r o m 4 2 C a ( a , a ' ) 4 2 C a [2] and 4 0 C a ( t , p ) 4 2 C a [3,4] e x p e r i m e n t s . A p r e l i m i n a r y r u n to d e t e r m i n e t h e s t a t e s e x c i t e d in the 41K(3He, d)42Ca r e a c t i o n w a s m a d e w i t h a m a g n e t i c s p e c t r o g r a p h and a thin ( ~ 5 0 ~ g / c m 2 ) KI t a r g e t , t h e s p e c t r u m b e i n g shown in fig. 1. T h e s t a t e s at 3.88 MeV and 4.05 MeV a r e w e a k l y e x c i t e d and in the a n a l y s i s of the s u b s e q u e n t d a t a t h e 3.88 MeV and 3.95 MeV l e v e l s w e r e a n a l y s e d a s one s t a t e a s w e r e the 4.05 MeV and 4.10 MeV s t a t e s . No p o s i t i v e p a r i t y e x c i t e d s t a t e s w e r e observed. A z e r o - r a n g e D W B A a n a l y s i s of t h e d a t a h a s b e e n c a r r i e d out u s i n g s u r f a c e a b s o r p t i o n in b o t h t h e 3He and d e u t e r o n o p t i c a l p o t e n t i a l s . N o n * This work has been entirely supported by grants from the Science Research Council.
l o c a l c o r r e c t i o n s in the e l a s t i c and b o u n d - s t a t e channels have been applied using the local energy a p p r o x i m a t i o n of P e r e y and Saxon [5]. Spin a s s i g n m e n t s of 3- h a v e b e e n m a d e [2,4] to t h e s t a t e s at 3.44 M e V , 4.68 MeV, 4.96 MeV and 5.66 MeV in 4 2 C a a s w e l l a s 5- to the 4.10 MeV l e v e l on the b a s i s of D W B A a n a l y s i s of t h e (a,a') and ( t , p ) data. Spin a s s i g n m e n t s to t h e 3.88 MeV, 4.90 MeV and 5.61 MeV l e v e l s of 1- w e r e m a d e on a p r e l i m i n a r y P W B A a n a l y s i s of t h e (t, p) d a t a Table 1 Spectroscopic information from the 41K(3He, d)42Ca reactions at 11.0 MeV. E x (~- 20 keY)
Sp
Ground 3.44 3.95 4.10
2.90 0.30 0.47 o.54
4.50 4.68 4.90 4.96
(2J+l) Sp
lp
J~
0+ 2.90 2.11 4.17 5.91
2 3 3 3
3(4)5-
0.36
1.78
3
(2)-
0.06 0.20 0.017
0.43 0.61 0.12
1 1 1
3(1)3-
5.07 5.15 5.41 5.52
0.093
0.60 0.17 0.33 0.65
1 1 1 1
( )( )( )3-
5.61 5.66
0.17 0.041
0.50 0.29
1 1
(1)3-
0.36
1
( )-
5.79
285
Volume 27B, n u m b e r 5
PHYSICS
LETTERS
5 A u g u s t 1968
°~
41K(3He,d)42Ca
~,
E3Ho= 11.0 MeV
400
0 = 20 ° ffi 3ko i.
tt
+!
E 300
E ~250 tm 200
o
J,
o
150
i 7
IO0 50
.-.J 0
260
i
.°.
280
/
] n
320
•, /
.]\ ........ " I
340 360 Distance along plate
"t....... •. . . . . 1 ,
380
,
• ...; ..... ....
400
1\ a
! "'"
;
u
/*20
;:\
-. .
x:~ ..............
i
...........
,
440
,
460
.
,
480
..I/
..2
~]
840
(mm)
Fig. 1. Deuteron s p e c t r u m taken at 0lab = 20 ° with a magnetic spectrograph. but were not considered conclusive when DWBA analysis was applied. T h e c o u p l i n g of a l d ~ p r o t o n h o l e to a l f ~ p r o t o n in 4 2 C a r e s u l t s i n a q u a r t e t of T = 1 s t a t e s of s p i n a n d p a r i t y 2 - , 3 - , 4 - a n d 5-. In t h e a b s e n c e of t h e i s o s p i n m i x i n g , t h e s u m r u l e s of M a c F a r l a n e a n d F r e n c h [6] g i v e a n e x p e c t e d s p e c t r o s c o p i c f a c t o r of S = 1.08 f o r e a c h of t h e s e f o u r lp = 3 t r a n s i t i o n s . On t h e b a s i s of t h e s p e c t r o s copic factors obtained from the DWBA analysis w e t e n t a t i v e l y a s s i g n s p i n s of 4 - a n d 2 - to t h e 3.95 a n d 4.50 M e V s t a t e s , r e s p e c t i v e l y . A n a s s i g n m e n t of 2 - t o t h e 3.95 M e V l e v e l w o u l d g i v e a l a r g e s p e c t r o s c o p i c f a c t o r of 0 . 8 4 ; s i m i l a r l y , a n a s s i g n m e n t of 4 - t o t h e 4 . 5 0 M e V l e v e l w o u l d l e a d to a low s p e c t r o s c o p i c f a c t o r of 0.20. If t h e s e s p i n a s s i g n m e n t s a r e c o r r e c t t h e 4 and 2- levels in 42Ca lie much lower in energy t h a n t h e s a m e two l e v e l s in 4 0 C a r e s u l t i n g in a c o n s i d e r a b l y r e d u c e d s p l i t t i n g of t h e 2 - , 3 - , 4 - , 5- q u a r t e t in 4 2 C a . The spectroscopic factors deduced for all the s t a t e s s e e n in 4 2 C a i n t h e p r e s e n t w o r k a r e g i v e n i n t a b l e 1. T h e s u m m e d s p e c t r o s c o p i c f a c t o r f o r t h e t h r e e v a l u e s of l p f o u n d in t h e 4 1 K ( 3 H e , d ) 4 2 C a r e a c t i o n a r e g i v e n in t a b l e 2 a n d a r e c o m p a r e d w i t h t h e s a m e s u m m e d f a c t o r s f o u n d in t h e 39K(3He, d ) 4 0 C a r e a c t i o n w h i c h w e h a v e a l s o m e a s u r e d a t t h e s a m e 3He b o m b a r d i n g e n e r g y . 286
Table 2 Comparison of spectroscopic factor sum rules in 40Ca and 42Ca. 42Ca
40Ca
lp=l lp=2
/p--3
~,(2J+1)Sp
9.45
5.83
19.10 4.05
~(2J+ 1)Sp expected
0.59
0.73
0.59
42Ca/40Ca
0.43
0.75
0.69
l=1
0.25
l =2 P
l =3 p
2.90
13.97
0.54
0.41
The spectroscopic factors for the 42Ca data are l o w e r in a l l c a s e s t h a n f o r t h e 4 0 C a d a t a b u t t h e ratio between the 42Ca and 40Ca results is cons t a n t w i t h i n t h e e r r o r s of t h e e x p e r i m e n t a l c r o s s sections. W e w i s h to t h a n k P r o f e s s o r L. L. G r e e n f o r h i s i n t e r e s t in t h i s w o r k a n d C. O. L e n n o n , J . L . D u r e l l a n d P. R. A l d e r s o n f o r a s s i s t a n c e in collecting the data.
\_
i
860
Volume 27B, n u m b e r 5
PHYSICS
References 1. J . L . A l t y , L . L . Green, R. Huby, G . D . J o n e s , J . R . M i n e s and J. F. S h a r p e y - S c h a f e r , Nucl. P h y s . 97 (1967) 541A. 2. E . P . Lippincott and A. M. B e r s t e i n , P h y s . Rev. 163 (1967) 1170. 3. D . C . W i l l i a m s , J . D . K n i g h t and W. T. Leland, P h y s . Rev. 164 (1967) 1419.
LETTERS
5 A u g u s t 1968
4. J . H . B j e r r e g a a r d , O. Hansen, O. Nathan, R. Chapm a n , S. Hinds and R. Middleton, Nucl. P h y s . A103 (1967) 33. 5. F. G. P e r e y and D. Saxon, P h y s . L e t t e r s 10 (1964) 107. 6. M.H. M a c F a r l a n e and J. B. F r e n c h , Revs. Mod. P h y s . 32 (1960) 567; J. B. F r e n c h and M. H. M a c F a r l a n e , Nucl. P h y s . 26 (1961) 168.
287
PHYSICS
PARTICLE BY THE
LETTERS
5 August 1968
HOLE STATES IN 42Ca EXCITED 41K(3He, d)42Ca REACTION*
J. S. F O R S T E R , K. B E A R P A R K , J. L. H U T T O N and J. F. S H A R P E Y - S C H A F E R
Chadwick Laboratory, University of Liverpool, UK Received 20 June 1968
P a r t i c l e hole states in 42Ca up to an excitation energy of 5.79 MeV have been determined. The quartet of states arising from the (ld~ -1, lf~) configuration has been identified and from the extracted spectroscopic factors spin assignments of 4- and 2- are made to the 3.95 MeV and 4.50 MeV levels.
T h e 41K(3He, d)42Ca r e a c t i o n h a s b e e n u s e d to i n v e s t i g a t e p a r t i c l e - h o l e s t a t e s in 4 2 C a f o r m e d b y c o u p l i n g a ld~ p r o t o n h o l e to a p r o t o n in t h e lf~ o r 2p s h e l l s ; t h e g r o u n d s t a t e of 41K i s e x p e c t e d to be m a i n l y a c l o s e d s - d s h e l l c o r e p l u s a l d ~ p r o t o n h o l e and two lf½ n e u t r o n s . T h e s t a t e s f o r m e d can b e T = 1 o r 2 s t a t e s ; the T = 2 s t a t e s a r e t h e a n a l o g u e s of s t a t e s in 42K and a r e e x p e c t e d to s t a r t at an e x c i t a t i o n e n e r g y of about 7.6 MeV in 42Ca. T h e e x p e r i m e n t w a s c a r r i e d out w i t h t h e 11.0 MeV 3He++ b e a m f r o m t h e L i v e r p o o l U n i v e r s i t y t a n d e m V a n de G r a a f f a c c e l e r a t o r . T h e r e a c t i o n d e u t e r o n s w e r e o b s e r v e d in a s u r f a c e barrier detector telescope with pulse multiplic a t i o n p a r t i c l e i d e n t i f i c a t i o n t e c h n i q u e s [1]. T h e t a r g e t s , e n r i c h e d to 95.35% in 41K, w e r e p r e p a r e d by e v a p o r a t i n g 2 0 0 ~ g / c m 2 of KI onto a thin c a r b o n b a c k i n g . T h e e r r o r in t h e e x p e r i m e n t a l a b s o l u t e c r o s s s e c t i o n s i s e s t i m a t e d to b e + 20%. T h e l e v e l s c h e m e of 4 2 C a h a s r e c e n t l y b e e n d e t e r m i n e d f r o m 4 2 C a ( a , a ' ) 4 2 C a [2] and 4 0 C a ( t , p ) 4 2 C a [3,4] e x p e r i m e n t s . A p r e l i m i n a r y r u n to d e t e r m i n e t h e s t a t e s e x c i t e d in the 41K(3He, d)42Ca r e a c t i o n w a s m a d e w i t h a m a g n e t i c s p e c t r o g r a p h and a thin ( ~ 5 0 ~ g / c m 2 ) KI t a r g e t , t h e s p e c t r u m b e i n g shown in fig. 1. T h e s t a t e s at 3.88 MeV and 4.05 MeV a r e w e a k l y e x c i t e d and in the a n a l y s i s of the s u b s e q u e n t d a t a t h e 3.88 MeV and 3.95 MeV l e v e l s w e r e a n a l y s e d a s one s t a t e a s w e r e the 4.05 MeV and 4.10 MeV s t a t e s . No p o s i t i v e p a r i t y e x c i t e d s t a t e s w e r e observed. A z e r o - r a n g e D W B A a n a l y s i s of t h e d a t a h a s b e e n c a r r i e d out u s i n g s u r f a c e a b s o r p t i o n in b o t h t h e 3He and d e u t e r o n o p t i c a l p o t e n t i a l s . N o n * This work has been entirely supported by grants from the Science Research Council.
l o c a l c o r r e c t i o n s in the e l a s t i c and b o u n d - s t a t e channels have been applied using the local energy a p p r o x i m a t i o n of P e r e y and Saxon [5]. Spin a s s i g n m e n t s of 3- h a v e b e e n m a d e [2,4] to t h e s t a t e s at 3.44 M e V , 4.68 MeV, 4.96 MeV and 5.66 MeV in 4 2 C a a s w e l l a s 5- to the 4.10 MeV l e v e l on the b a s i s of D W B A a n a l y s i s of t h e (a,a') and ( t , p ) data. Spin a s s i g n m e n t s to t h e 3.88 MeV, 4.90 MeV and 5.61 MeV l e v e l s of 1- w e r e m a d e on a p r e l i m i n a r y P W B A a n a l y s i s of t h e (t, p) d a t a Table 1 Spectroscopic information from the 41K(3He, d)42Ca reactions at 11.0 MeV. E x (~- 20 keY)
Sp
Ground 3.44 3.95 4.10
2.90 0.30 0.47 o.54
4.50 4.68 4.90 4.96
(2J+l) Sp
lp
J~
0+ 2.90 2.11 4.17 5.91
2 3 3 3
3(4)5-
0.36
1.78
3
(2)-
0.06 0.20 0.017
0.43 0.61 0.12
1 1 1
3(1)3-
5.07 5.15 5.41 5.52
0.093
0.60 0.17 0.33 0.65
1 1 1 1
( )( )( )3-
5.61 5.66
0.17 0.041
0.50 0.29
1 1
(1)3-
0.36
1
( )-
5.79
285
Volume 27B, n u m b e r 5
PHYSICS
LETTERS
5 A u g u s t 1968
°~
41K(3He,d)42Ca
~,
E3Ho= 11.0 MeV
400
0 = 20 ° ffi 3ko i.
tt
+!
E 300
E ~250 tm 200
o
J,
o
150
i 7
IO0 50
.-.J 0
260
i
.°.
280
/
] n
320
•, /
.]\ ........ " I
340 360 Distance along plate
"t....... •. . . . . 1 ,
380
,
• ...; ..... ....
400
1\ a
! "'"
;
u
/*20
;:\
-. .
x:~ ..............
i
...........
,
440
,
460
.
,
480
..I/
..2
~]
840
(mm)
Fig. 1. Deuteron s p e c t r u m taken at 0lab = 20 ° with a magnetic spectrograph. but were not considered conclusive when DWBA analysis was applied. T h e c o u p l i n g of a l d ~ p r o t o n h o l e to a l f ~ p r o t o n in 4 2 C a r e s u l t s i n a q u a r t e t of T = 1 s t a t e s of s p i n a n d p a r i t y 2 - , 3 - , 4 - a n d 5-. In t h e a b s e n c e of t h e i s o s p i n m i x i n g , t h e s u m r u l e s of M a c F a r l a n e a n d F r e n c h [6] g i v e a n e x p e c t e d s p e c t r o s c o p i c f a c t o r of S = 1.08 f o r e a c h of t h e s e f o u r lp = 3 t r a n s i t i o n s . On t h e b a s i s of t h e s p e c t r o s copic factors obtained from the DWBA analysis w e t e n t a t i v e l y a s s i g n s p i n s of 4 - a n d 2 - to t h e 3.95 a n d 4.50 M e V s t a t e s , r e s p e c t i v e l y . A n a s s i g n m e n t of 2 - t o t h e 3.95 M e V l e v e l w o u l d g i v e a l a r g e s p e c t r o s c o p i c f a c t o r of 0 . 8 4 ; s i m i l a r l y , a n a s s i g n m e n t of 4 - t o t h e 4 . 5 0 M e V l e v e l w o u l d l e a d to a low s p e c t r o s c o p i c f a c t o r of 0.20. If t h e s e s p i n a s s i g n m e n t s a r e c o r r e c t t h e 4 and 2- levels in 42Ca lie much lower in energy t h a n t h e s a m e two l e v e l s in 4 0 C a r e s u l t i n g in a c o n s i d e r a b l y r e d u c e d s p l i t t i n g of t h e 2 - , 3 - , 4 - , 5- q u a r t e t in 4 2 C a . The spectroscopic factors deduced for all the s t a t e s s e e n in 4 2 C a i n t h e p r e s e n t w o r k a r e g i v e n i n t a b l e 1. T h e s u m m e d s p e c t r o s c o p i c f a c t o r f o r t h e t h r e e v a l u e s of l p f o u n d in t h e 4 1 K ( 3 H e , d ) 4 2 C a r e a c t i o n a r e g i v e n in t a b l e 2 a n d a r e c o m p a r e d w i t h t h e s a m e s u m m e d f a c t o r s f o u n d in t h e 39K(3He, d ) 4 0 C a r e a c t i o n w h i c h w e h a v e a l s o m e a s u r e d a t t h e s a m e 3He b o m b a r d i n g e n e r g y . 286
Table 2 Comparison of spectroscopic factor sum rules in 40Ca and 42Ca. 42Ca
40Ca
lp=l lp=2
/p--3
~,(2J+1)Sp
9.45
5.83
19.10 4.05
~(2J+ 1)Sp expected
0.59
0.73
0.59
42Ca/40Ca
0.43
0.75
0.69
l=1
0.25
l =2 P
l =3 p
2.90
13.97
0.54
0.41
The spectroscopic factors for the 42Ca data are l o w e r in a l l c a s e s t h a n f o r t h e 4 0 C a d a t a b u t t h e ratio between the 42Ca and 40Ca results is cons t a n t w i t h i n t h e e r r o r s of t h e e x p e r i m e n t a l c r o s s sections. W e w i s h to t h a n k P r o f e s s o r L. L. G r e e n f o r h i s i n t e r e s t in t h i s w o r k a n d C. O. L e n n o n , J . L . D u r e l l a n d P. R. A l d e r s o n f o r a s s i s t a n c e in collecting the data.
\_
i
860
Volume 27B, n u m b e r 5
PHYSICS
References 1. J . L . A l t y , L . L . Green, R. Huby, G . D . J o n e s , J . R . M i n e s and J. F. S h a r p e y - S c h a f e r , Nucl. P h y s . 97 (1967) 541A. 2. E . P . Lippincott and A. M. B e r s t e i n , P h y s . Rev. 163 (1967) 1170. 3. D . C . W i l l i a m s , J . D . K n i g h t and W. T. Leland, P h y s . Rev. 164 (1967) 1419.
LETTERS
5 A u g u s t 1968
4. J . H . B j e r r e g a a r d , O. Hansen, O. Nathan, R. Chapm a n , S. Hinds and R. Middleton, Nucl. P h y s . A103 (1967) 33. 5. F. G. P e r e y and D. Saxon, P h y s . L e t t e r s 10 (1964) 107. 6. M.H. M a c F a r l a n e and J. B. F r e n c h , Revs. Mod. P h y s . 32 (1960) 567; J. B. F r e n c h and M. H. M a c F a r l a n e , Nucl. P h y s . 26 (1961) 168.
287