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DWBA and the 3.12 MeV state in 60Ni
Volume 28B, number 8
PHYSICS
DWBA
AND
THE
3.12
LETTERS
MeV
3 February 1969
STATE
IN
60Ni
R. K. J O L L Y , M . D . G O L D B E R G * and A. K. S E N G U P T A ** A . E . R . E . , Harwell, U.K. W. D A R C E Y University of Oxford, U.K. R. CHAPMAN$ and S. HINDS $$ A. W . R . E . , Alderrnaston, U.K.
Received 3 January 1969
The apparent inconsistency and failure of DWBA analyses applied to (d, d r) angular distribution data for the 3.12 MeV state of 60Ni, measured at E d = 11.5 MeV and 14.8 MeV, are explained by (t,p) m e a s u r e ments which suggest that the state is a 2 +, 4 + doublet.
It h a s b e e n f i r m l y e s t a b l i s h e d by s e v e r a l w o r k e r s [1-3] that t h e r e i s a s t a t e at 3.12 MeV in 60Ni w i t h spin and p a r i t y 2 +. H o w e v e r , D W B A a n a l y s i s of 60Ni(d, d') d a t a m e a s u r e d by J o l l y e t al. at E d = 14.8 MeV ( r e s o l u t i o n 55 keV) [4] and, m o r e r e c e n t l y , at E d = 11.5 MeV w i t h i m p r o v e d e n e r g y r e s o l u t i o n (~ 25 keV) [5] did not a g r e e w i t h the a c c e p t e d spin and p a r i t y a s s i g n m e n t s f o r t h i s s t a t e . I n d e e d the (d, d') d a t a at E d = 14.8 MeV a p p e a r e d to b e c o n s i s t e n t w i t h a s p i n and p a r i t y of 3- (fig. 1 top), w h i l e the a g r e e m e n t w i t h l = 2 and l = 3 w a s p o o r f o r the 11.5 MeV d a t a (fig. 1 b o t t o m ) . T h e a p p a r e n t i n c o n s i s t e n c y and f a i l u r e of DWBA a n a l y s i s in t h i s c a s e r u n c o n t r a r y to the s u c c e s s n o r m a l l y e x p e r i e n c e d w i t h (d, d') d a t a at t h e s e b o m b a r d i n g e n e r g i e s and in t h i s m a s s r e g i o n [6]. S i n c e the s t a t e i s s t r o n g l y e x c i t e d in i n e l a s t i c d e u t e r o n s c a t t e r i n g , it s e e m s r e a s o n a b l e to a s s u m e t h a t it i s not c o m p l e x in n a t u r e and should f a l l w i t h i n the r a n g e of a p p l i c a b i l i t y of c o n v e n t i o n a l DWBA a n a l y s i s i n v o k i n g a o n e - s t e p a n g u l a r m o m e n t u m t r a n s f e r p r o c e s s . Of c o u r s e , one p o s s i b l e e x p l a n a t i o n f o r the f a i l u r e in t h i s c a s e i s t h a t the l e v e l at 3.12 MeV i s a m u l t i p l e t [7]. H o w e v e r , no m u l t i p l e t s t r u c t u r e w a s o b s e r v e d in the p r e s e n t (d. d') w o r k o r in r e c e n t high r e s o l u tion (11 keV) ~0Ni(p, p') m e a s u r e m e n t s [8]. 0
* Present address: USA. ** Present address: ~Present address: ~ P r e s e n t address: Daresbury. 546
Brookhaven National Laboratory, Saha Institute, Calcutta, India. A. E. R.E., Harwell. Nuclear Physics Laboratory,
20
40
60
80
I00
ANGLE (C. of M~ DEGREES
Fig. 1. D e u t e r o n a n g u l a r d i s t r i b u t i o n s f o r the 3.12 MeV
state in 60Ni and their comparison with I = 3 cross sections and combinations of l= 2 and 4 cross sections calculated with the DWBA code JULIE.
Volume 28B, n u m b e r 8
PHYSICS
LETTERS
bination except l = 2 and l = 4 described the data s a t i s f a c t o r i l y (fig. 1 b o t t o m ) . In t h e c a s e of t h e 14.8 M e V (d, d ' ) a n g u l a r d i s t r i b u t i o n [4] t h e c o m b i n a t i o n of l = 2 a n d l = 4 D W B A c a l c u l a t i o n s f i t s t h e e x p e r i m e n t a l d a t a a l i t t l e b e t t e r t h a n l= 3 (fig. 1 top). It i s n o t e w o r t h y t h a t , a s e x p e c t e d , b o t h s e t s of (d, d ' ) d a t a h a v e b e e n s u c c e s s f u l l y f i t t e d w i t h t h e s a m e r a t i o of l = 2 a n d l = 4 p e a k cross sections. T h u s , i n t h e c o n t e x t of t h e c o n c l u s i o n s f r o m ( t , p ) s t u d i e s i . e . t h e 3.12 M e V s t a t e i s a 2 +, 4 + doublet, DWBA analyses consistently explain both s e t s of (d, d ' ) d a t a .
3.12 MeV STATE
I/I IEXPT.
n, ee b
Lv 3O
60
9O
3 F e b r u a r y 1969
L 120
T h e a u t h o r s a r e i n d e b t e d to D r . R. M. D r i s k o f o r l e n d i n g t h e m a c o p y of t h e D W B A c o d e J U L I E .
ANGLE (C. of M.) DEGREES Fig. 2. Decomposition of the 3.12 MeV state proton angular distribution into those for Z = 2 and 4 t r a n s i t i o n s in the 58Ni(t,p)60Ni r e a c t i o n m e a s u r e d at E t = 12 MeV. R e c e n t l y s o m e 58Ni(t, p ) 6 0 N i m e a s u r e m e n t s h a v e b e e n m a d e a t A l d e r m a s t o n [9] ( E t = 12 M e V , r e s o l u t i o n 15 k e V ) a n d o n c e a g a i n t h e r e w a s n o direct evidence for multiplet structure in the 3.12 M e V s t a t e . It h a s b e e n d e m o n s t r a t e d e a r l i e r [9, 10] t h a t p r o t o n a n g u l a r d i s t r i b u t i o n s a r e v e r y c h a r a c t e r i s t i c of t h e a n g u l a r m o m e n t u m t r a n s f e r i n t h e (t, p) r e a c t i o n s i n t h i s m a s s r e g i o n . H o w e v e r i n t h e c a s e of t h e 3.12 M e V s t a t e i t w a s found that the data could be described only by a s u i t a b l e l i n e a r c o m b i n a t i o n of l = 2 a n d l = 4 a n g u l a r d i s t r i b u t i o n s t a k e n f r o m (t, p) s t u d i e s a t t h i s e n e r g y o n Ni i s o t o p e s to w e l l a u t h e n t i c a t e d 2 + a n d 4 + s t a t e s (fig. 2). T h e s a m e p r o c e d u r e w a s t r i e d o n t h e 11.5 M e V (d, d ' ) a n g u l a r d i s t r i bution when it was found that no permissible corn-
References 1. R.H. F u l m e r and W. W. Daehnick, Phys. Rev. 139 (1965) B579. 2. R.K. Mohindra.and D. M. Van P a t t e r , Phys. Rev . 139 (1965) H274; S. M. Shaffroth and G. T. Wood, Phys. Rev. 149 (1966) 827. 3. C, M. L e d e r e r , J.M. Hollander and I. P e r l m a n , Table of I s o t o p e s - s i x t h edition (John Wiley and Sons, Inc., 1967). 4. R . K . J o l l y , Phys, Rev. 139 (1965) B318. 5. R, K. Jolly, M.D. Goldberg and A. K. SenGupta, Nucl. Phys., to be published. 6. R.K. Jolly, M.D. Goldberg, A.K. SenGupta, AERE Report-R5798. 7. R. G. Tee and A. Aspinall, Nucl. Phys. A98 (1967) 417. 8. W. Darcey. R. Chapman and S. Hinds, to be s u b m i t ted to Nucl. Phys. 9. J . H . B j e r r e g a a r d et al., Nucl. Phys. A103 (1967) 33.
* * * * *
547
PHYSICS
DWBA
AND
THE
3.12
LETTERS
MeV
3 February 1969
STATE
IN
60Ni
R. K. J O L L Y , M . D . G O L D B E R G * and A. K. S E N G U P T A ** A . E . R . E . , Harwell, U.K. W. D A R C E Y University of Oxford, U.K. R. CHAPMAN$ and S. HINDS $$ A. W . R . E . , Alderrnaston, U.K.
Received 3 January 1969
The apparent inconsistency and failure of DWBA analyses applied to (d, d r) angular distribution data for the 3.12 MeV state of 60Ni, measured at E d = 11.5 MeV and 14.8 MeV, are explained by (t,p) m e a s u r e ments which suggest that the state is a 2 +, 4 + doublet.
It h a s b e e n f i r m l y e s t a b l i s h e d by s e v e r a l w o r k e r s [1-3] that t h e r e i s a s t a t e at 3.12 MeV in 60Ni w i t h spin and p a r i t y 2 +. H o w e v e r , D W B A a n a l y s i s of 60Ni(d, d') d a t a m e a s u r e d by J o l l y e t al. at E d = 14.8 MeV ( r e s o l u t i o n 55 keV) [4] and, m o r e r e c e n t l y , at E d = 11.5 MeV w i t h i m p r o v e d e n e r g y r e s o l u t i o n (~ 25 keV) [5] did not a g r e e w i t h the a c c e p t e d spin and p a r i t y a s s i g n m e n t s f o r t h i s s t a t e . I n d e e d the (d, d') d a t a at E d = 14.8 MeV a p p e a r e d to b e c o n s i s t e n t w i t h a s p i n and p a r i t y of 3- (fig. 1 top), w h i l e the a g r e e m e n t w i t h l = 2 and l = 3 w a s p o o r f o r the 11.5 MeV d a t a (fig. 1 b o t t o m ) . T h e a p p a r e n t i n c o n s i s t e n c y and f a i l u r e of DWBA a n a l y s i s in t h i s c a s e r u n c o n t r a r y to the s u c c e s s n o r m a l l y e x p e r i e n c e d w i t h (d, d') d a t a at t h e s e b o m b a r d i n g e n e r g i e s and in t h i s m a s s r e g i o n [6]. S i n c e the s t a t e i s s t r o n g l y e x c i t e d in i n e l a s t i c d e u t e r o n s c a t t e r i n g , it s e e m s r e a s o n a b l e to a s s u m e t h a t it i s not c o m p l e x in n a t u r e and should f a l l w i t h i n the r a n g e of a p p l i c a b i l i t y of c o n v e n t i o n a l DWBA a n a l y s i s i n v o k i n g a o n e - s t e p a n g u l a r m o m e n t u m t r a n s f e r p r o c e s s . Of c o u r s e , one p o s s i b l e e x p l a n a t i o n f o r the f a i l u r e in t h i s c a s e i s t h a t the l e v e l at 3.12 MeV i s a m u l t i p l e t [7]. H o w e v e r , no m u l t i p l e t s t r u c t u r e w a s o b s e r v e d in the p r e s e n t (d. d') w o r k o r in r e c e n t high r e s o l u tion (11 keV) ~0Ni(p, p') m e a s u r e m e n t s [8]. 0
* Present address: USA. ** Present address: ~Present address: ~ P r e s e n t address: Daresbury. 546
Brookhaven National Laboratory, Saha Institute, Calcutta, India. A. E. R.E., Harwell. Nuclear Physics Laboratory,
20
40
60
80
I00
ANGLE (C. of M~ DEGREES
Fig. 1. D e u t e r o n a n g u l a r d i s t r i b u t i o n s f o r the 3.12 MeV
state in 60Ni and their comparison with I = 3 cross sections and combinations of l= 2 and 4 cross sections calculated with the DWBA code JULIE.
Volume 28B, n u m b e r 8
PHYSICS
LETTERS
bination except l = 2 and l = 4 described the data s a t i s f a c t o r i l y (fig. 1 b o t t o m ) . In t h e c a s e of t h e 14.8 M e V (d, d ' ) a n g u l a r d i s t r i b u t i o n [4] t h e c o m b i n a t i o n of l = 2 a n d l = 4 D W B A c a l c u l a t i o n s f i t s t h e e x p e r i m e n t a l d a t a a l i t t l e b e t t e r t h a n l= 3 (fig. 1 top). It i s n o t e w o r t h y t h a t , a s e x p e c t e d , b o t h s e t s of (d, d ' ) d a t a h a v e b e e n s u c c e s s f u l l y f i t t e d w i t h t h e s a m e r a t i o of l = 2 a n d l = 4 p e a k cross sections. T h u s , i n t h e c o n t e x t of t h e c o n c l u s i o n s f r o m ( t , p ) s t u d i e s i . e . t h e 3.12 M e V s t a t e i s a 2 +, 4 + doublet, DWBA analyses consistently explain both s e t s of (d, d ' ) d a t a .
3.12 MeV STATE
I/I IEXPT.
n, ee b
Lv 3O
60
9O
3 F e b r u a r y 1969
L 120
T h e a u t h o r s a r e i n d e b t e d to D r . R. M. D r i s k o f o r l e n d i n g t h e m a c o p y of t h e D W B A c o d e J U L I E .
ANGLE (C. of M.) DEGREES Fig. 2. Decomposition of the 3.12 MeV state proton angular distribution into those for Z = 2 and 4 t r a n s i t i o n s in the 58Ni(t,p)60Ni r e a c t i o n m e a s u r e d at E t = 12 MeV. R e c e n t l y s o m e 58Ni(t, p ) 6 0 N i m e a s u r e m e n t s h a v e b e e n m a d e a t A l d e r m a s t o n [9] ( E t = 12 M e V , r e s o l u t i o n 15 k e V ) a n d o n c e a g a i n t h e r e w a s n o direct evidence for multiplet structure in the 3.12 M e V s t a t e . It h a s b e e n d e m o n s t r a t e d e a r l i e r [9, 10] t h a t p r o t o n a n g u l a r d i s t r i b u t i o n s a r e v e r y c h a r a c t e r i s t i c of t h e a n g u l a r m o m e n t u m t r a n s f e r i n t h e (t, p) r e a c t i o n s i n t h i s m a s s r e g i o n . H o w e v e r i n t h e c a s e of t h e 3.12 M e V s t a t e i t w a s found that the data could be described only by a s u i t a b l e l i n e a r c o m b i n a t i o n of l = 2 a n d l = 4 a n g u l a r d i s t r i b u t i o n s t a k e n f r o m (t, p) s t u d i e s a t t h i s e n e r g y o n Ni i s o t o p e s to w e l l a u t h e n t i c a t e d 2 + a n d 4 + s t a t e s (fig. 2). T h e s a m e p r o c e d u r e w a s t r i e d o n t h e 11.5 M e V (d, d ' ) a n g u l a r d i s t r i bution when it was found that no permissible corn-
References 1. R.H. F u l m e r and W. W. Daehnick, Phys. Rev. 139 (1965) B579. 2. R.K. Mohindra.and D. M. Van P a t t e r , Phys. Rev . 139 (1965) H274; S. M. Shaffroth and G. T. Wood, Phys. Rev. 149 (1966) 827. 3. C, M. L e d e r e r , J.M. Hollander and I. P e r l m a n , Table of I s o t o p e s - s i x t h edition (John Wiley and Sons, Inc., 1967). 4. R . K . J o l l y , Phys, Rev. 139 (1965) B318. 5. R, K. Jolly, M.D. Goldberg and A. K. SenGupta, Nucl. Phys., to be published. 6. R.K. Jolly, M.D. Goldberg, A.K. SenGupta, AERE Report-R5798. 7. R. G. Tee and A. Aspinall, Nucl. Phys. A98 (1967) 417. 8. W. Darcey. R. Chapman and S. Hinds, to be s u b m i t ted to Nucl. Phys. 9. J . H . B j e r r e g a a r d et al., Nucl. Phys. A103 (1967) 33.
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547