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Triple coincidence measurements in the decay of 48V
V a n Nooijen, B. K o n i j n , J. W a p s t r a , A. H.
Physica XXIV 231-232
LETTER Triple
coincidence
TO THE
EDITOR
measurements
in the decay
o f 48V
T h e 16d 4s V isotope d e c a y s to 48Ti b y e l e c t r o n c a p t u r e a n d p o s i t o n emission followed b y g a m m a r a y s as d e p i c t e d in fig. 1 z)2)3)4)5)8). C a s s o n et alii 5) r e p o r t e d triple coincidences b e t w e e n ? r a y s a n d e x p l a i n e d t h e m as b e i n g due t o a 0.94 MeV g a m m a r a y of ( 1 0 - t - 5 ) % i n t e n s i t y b e t w e e n t h e 3.24 M e V a n d 2.30 M e V levels. T h e o t h e r e x p l a n a t i o n g i v e n b y C a s s o n et alii, viz. t h a t t h e s e coincidences were due to a ? r a y b e t w e e n t h e 3.34 MeV (6 +) level a n d t h e 2.30 MeV level c a n n o w b e e x c l u d e d 6)7.)16). 4+ ECo_
4.020 .~'48
V
2.25..
/.+ 2.3.00
.eV 56.0 %
1.31HeV 97% 2+
0.995
0.99 HI~V O+
49-1-i
Fig. 1. D e c a y s c h e m e of 48V. R e c e n t l y t h e elfl + b r a n c h i n g r a t i o was m e a s u r e d in t h i s l a b o r a t o r y . A s s u m i n g n o 0.94 MeV ? r a y t o b e p r e s e n t , t h e r a t i o in t h e t r a n s i t i o n t o t h e 2.30 M e V level as m e a s u r e d in t w o i n d e p e n d e n t w a y s was 0.75 -4- 0.03 6) a n d 0.74 :t: 0.02 s) ; in excellent a g r e e m e n t w i t h t h e t h e o r e t i c a l v a l u e 0.76 9)10)11). Since o t h e r m e a s u r e m e n t s o n e/fl + b r a n c h i n g r a t i o s 12)13)la) also show excellent a g r e e m e n t w i t h t h e o r y , one can, reversely, c o m p u t e f r o m t h i s r e s u l t 14) t h a t t h e i n t e n s i t y of t h e 0.94 MeV ? r a y s h o u l d b e (0 q- 2) %. W e t h e r e f o r e r e p e a t e d t h e triple coincidence m e a s u r e m e n t s . T h e ? r a y s were m e a s u r e d in t h r e e NaI(TI) s c i n t i l l a t i o n s p e c t r o m e t e r c h a n n e l s ; c h a n n e l A a c c e p t e d t h e 1.3 MeV p h o t o p e a k o n l y ; t h e o t h e r c h a n n e l s B a n d C t h e region of 0.99 a n d 0.94 M e V p h o t o p e a k s . Triple coincidences were m e a s u r e d b y a c o m b i n a t i o n d o u b l e coincidence circuits; t h e resolving t i m e s for (A, B) coincidences was TAB = = 2 × l0 -8 sec. for (B, C) coincidences ZBC = 5 X l0 -7 sec. I n o r d e r to c o m p u t e c o r r e c t i o n s for a c c i d e n t a l triple coincidences, coincidences AC were also m e a s u r e d w i t h TAC = 3 × 10 -Tsec. --
231
--
232
TRIPLE COINCIDENCE MEASUREMENTS IN THE DECAY OF 48V
T h e n u m b e r of t r i p l e coincidences in a 136 h o u r s r u n a g r e e d witti t h e c o m p u t e d n u m b e r of a c c i d e n t a l coincidences. T h e i n t e n s i t y of t h e 0.94 M e V ~ r a y c o m p u t e d f r o m o u r r e s u l t is ( - - 2 . 6 4- 3.0) % m e a n i n g t h a t t h e r e is o n l y 1% c h a n c e t h a t t h e i n t e n s i t y of t h i s t r a n s i t i o n is l a r g e r t h a n 4 . 5 % . T h e possible i n f l u e n c e of a n n i h i l a t i o n in f l i g h t h a s n o t b e e n t a k e n i n t o a c c o u n t , b u t could a t m o s t o n l y decrease t h i s value. T h e i n t e n s i t y r a t i o of t h e 0.94 M e V M1 V r a y a n d t h e 2.25 M e V E 2 one a c c o r d i n g t o t h e W e i s s k o p f e s t i m a t e is 30, a n d a c c o r d i n g t o Our m e a s u r e m e n t less ( p r o b a b l y m u c h less), t h a n 2. T h i s c a n b e e x p l a i n e d in t h e following way. A c c o r d i n g to S h e l i n e 15), s t r o n g d e f o r m a t i o n s c a n o c c u r in 48Ti. W e c a n t h e r e f o r e e x p e c t v i b r a t i o n a l a n d r o t a t i o n a l b a n d s . T h e r a t i o of t h e e x c i t a t i o n energies of t h e 0.99, 2.30 a n d 3.34 M e V levels agrees r e a s o n a b l y w i t h a v i b r a t i o n a l b a n d , t h a t of t h e 0.99 a n d 3.24 M e V w i t h a r o t a t i o n a l one. T h u s one e x p e c t s t h e 0.99 M e V level to b e a m i x t u r e h a v i n g p a r t l y v i b r a t i o n a l , p a r t l y r o t a t i o n a l c h a r a c t e r ; since, h o w e v e r , t h e 2.30 a n d 3.24 M e V levels a r e f a r a p a r t , t h e y m a y b e m u c h purer. I n t h a t case t h e possible M1 r r a y bet~veen t h e m m a y b e c o n s i d e r a b l y r e t a r d e d , w h e r e a s t h e E 2 ~ r a y b e t w e e n t h e t w o s t a t e s of t h e r o t a t i o n a l b a n d will e v e n b e e n h a n c e d : T h e helpful discussions w i t h Dr. R. V a n L i e s h o u t is g r a t e f u l l y a c k n o w l e d g e d . T h e a u t h o r s are i n d e b t e d t o Prof. Dr. A. H. W. A t e n Jr. a n d Mrs. A. C. F u n k e K l o p p e r for t h e c h e m i c a l s e p a r a t i o n a n d to t h e s t a f f of t h e P h i l i p s s y n c h r o - c y c l o t r o n in A m s t e r d a m for t h e i r r a d i a t i o n s . B. VAN NOOIJEN J. KONIJN A. H. ~VAPSTRA Laboratorium voor technische Fysica, Technische Hogeschool, Delft, Nederland Received 21-2-58. REFERENCES 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14) 15) 16)
Good, P e a s l e e and D e u t s c h , Phys. Rev. 69 (1946) 313. Ticho, G r e e n and R i c h a r d s o n , Phys. Rev. 86 (1952) 422. R o g g e n k a m p , P r u e t t and W i l k i n s o n , Phys. Rev. 88 (1952) 1262. S t e r k , W a p s t r a and K r o p v e l d , Physica 19 (1953) 135. Casson, G o o d m a n and K r o h n , Phys. Rev. 92 (1953) 1517. V a n Nooijen, Konijn, H e y l i g e r s , V. D. B r u g g e and W a p s t r a , Physica 23 (1957) 753. V a n L i e s h o u t , G r e e n b e r g , K o e r t s and Wu, Phys. Rev. 100 (1955) 223. H a g e d o o r n , H. L. and Konijn, J., Physica 23 {1957} 1069. Zweifel, P. F., Phys. Rev. 107 (1957) 329. Rose, M. E. and J a c k s o n , J. L., Phys. Rev. 76 (1949) 1540. W a p s t r a , Nijgh and Van L i e s h o u t , ,,Nuclear Spectroscopy Tables" North Holland Publishing Company, Amsterdam. In preparation. S h e r r , R. and Miller, R. H., Phys. Rev. 93 (1954) 1076. D r e v e r , M o l j k and Scobie, Phil. Mag. I (1956) 942. Konijn, H a g e d o o r n , V a n Nooijen and W a p s t r a , Nucl. Phys., to be published. S h e l i n e , R. K., Nucl. Phys. 2 (1956) 382. B o e h m , F. and W a p s t r a , A. H., Phys. Rev., to be published.
Physica XXIV 231-232
LETTER Triple
coincidence
TO THE
EDITOR
measurements
in the decay
o f 48V
T h e 16d 4s V isotope d e c a y s to 48Ti b y e l e c t r o n c a p t u r e a n d p o s i t o n emission followed b y g a m m a r a y s as d e p i c t e d in fig. 1 z)2)3)4)5)8). C a s s o n et alii 5) r e p o r t e d triple coincidences b e t w e e n ? r a y s a n d e x p l a i n e d t h e m as b e i n g due t o a 0.94 MeV g a m m a r a y of ( 1 0 - t - 5 ) % i n t e n s i t y b e t w e e n t h e 3.24 M e V a n d 2.30 M e V levels. T h e o t h e r e x p l a n a t i o n g i v e n b y C a s s o n et alii, viz. t h a t t h e s e coincidences were due to a ? r a y b e t w e e n t h e 3.34 MeV (6 +) level a n d t h e 2.30 MeV level c a n n o w b e e x c l u d e d 6)7.)16). 4+ ECo_
4.020 .~'48
V
2.25..
/.+ 2.3.00
.eV 56.0 %
1.31HeV 97% 2+
0.995
0.99 HI~V O+
49-1-i
Fig. 1. D e c a y s c h e m e of 48V. R e c e n t l y t h e elfl + b r a n c h i n g r a t i o was m e a s u r e d in t h i s l a b o r a t o r y . A s s u m i n g n o 0.94 MeV ? r a y t o b e p r e s e n t , t h e r a t i o in t h e t r a n s i t i o n t o t h e 2.30 M e V level as m e a s u r e d in t w o i n d e p e n d e n t w a y s was 0.75 -4- 0.03 6) a n d 0.74 :t: 0.02 s) ; in excellent a g r e e m e n t w i t h t h e t h e o r e t i c a l v a l u e 0.76 9)10)11). Since o t h e r m e a s u r e m e n t s o n e/fl + b r a n c h i n g r a t i o s 12)13)la) also show excellent a g r e e m e n t w i t h t h e o r y , one can, reversely, c o m p u t e f r o m t h i s r e s u l t 14) t h a t t h e i n t e n s i t y of t h e 0.94 MeV ? r a y s h o u l d b e (0 q- 2) %. W e t h e r e f o r e r e p e a t e d t h e triple coincidence m e a s u r e m e n t s . T h e ? r a y s were m e a s u r e d in t h r e e NaI(TI) s c i n t i l l a t i o n s p e c t r o m e t e r c h a n n e l s ; c h a n n e l A a c c e p t e d t h e 1.3 MeV p h o t o p e a k o n l y ; t h e o t h e r c h a n n e l s B a n d C t h e region of 0.99 a n d 0.94 M e V p h o t o p e a k s . Triple coincidences were m e a s u r e d b y a c o m b i n a t i o n d o u b l e coincidence circuits; t h e resolving t i m e s for (A, B) coincidences was TAB = = 2 × l0 -8 sec. for (B, C) coincidences ZBC = 5 X l0 -7 sec. I n o r d e r to c o m p u t e c o r r e c t i o n s for a c c i d e n t a l triple coincidences, coincidences AC were also m e a s u r e d w i t h TAC = 3 × 10 -Tsec. --
231
--
232
TRIPLE COINCIDENCE MEASUREMENTS IN THE DECAY OF 48V
T h e n u m b e r of t r i p l e coincidences in a 136 h o u r s r u n a g r e e d witti t h e c o m p u t e d n u m b e r of a c c i d e n t a l coincidences. T h e i n t e n s i t y of t h e 0.94 M e V ~ r a y c o m p u t e d f r o m o u r r e s u l t is ( - - 2 . 6 4- 3.0) % m e a n i n g t h a t t h e r e is o n l y 1% c h a n c e t h a t t h e i n t e n s i t y of t h i s t r a n s i t i o n is l a r g e r t h a n 4 . 5 % . T h e possible i n f l u e n c e of a n n i h i l a t i o n in f l i g h t h a s n o t b e e n t a k e n i n t o a c c o u n t , b u t could a t m o s t o n l y decrease t h i s value. T h e i n t e n s i t y r a t i o of t h e 0.94 M e V M1 V r a y a n d t h e 2.25 M e V E 2 one a c c o r d i n g t o t h e W e i s s k o p f e s t i m a t e is 30, a n d a c c o r d i n g t o Our m e a s u r e m e n t less ( p r o b a b l y m u c h less), t h a n 2. T h i s c a n b e e x p l a i n e d in t h e following way. A c c o r d i n g to S h e l i n e 15), s t r o n g d e f o r m a t i o n s c a n o c c u r in 48Ti. W e c a n t h e r e f o r e e x p e c t v i b r a t i o n a l a n d r o t a t i o n a l b a n d s . T h e r a t i o of t h e e x c i t a t i o n energies of t h e 0.99, 2.30 a n d 3.34 M e V levels agrees r e a s o n a b l y w i t h a v i b r a t i o n a l b a n d , t h a t of t h e 0.99 a n d 3.24 M e V w i t h a r o t a t i o n a l one. T h u s one e x p e c t s t h e 0.99 M e V level to b e a m i x t u r e h a v i n g p a r t l y v i b r a t i o n a l , p a r t l y r o t a t i o n a l c h a r a c t e r ; since, h o w e v e r , t h e 2.30 a n d 3.24 M e V levels a r e f a r a p a r t , t h e y m a y b e m u c h purer. I n t h a t case t h e possible M1 r r a y bet~veen t h e m m a y b e c o n s i d e r a b l y r e t a r d e d , w h e r e a s t h e E 2 ~ r a y b e t w e e n t h e t w o s t a t e s of t h e r o t a t i o n a l b a n d will e v e n b e e n h a n c e d : T h e helpful discussions w i t h Dr. R. V a n L i e s h o u t is g r a t e f u l l y a c k n o w l e d g e d . T h e a u t h o r s are i n d e b t e d t o Prof. Dr. A. H. W. A t e n Jr. a n d Mrs. A. C. F u n k e K l o p p e r for t h e c h e m i c a l s e p a r a t i o n a n d to t h e s t a f f of t h e P h i l i p s s y n c h r o - c y c l o t r o n in A m s t e r d a m for t h e i r r a d i a t i o n s . B. VAN NOOIJEN J. KONIJN A. H. ~VAPSTRA Laboratorium voor technische Fysica, Technische Hogeschool, Delft, Nederland Received 21-2-58. REFERENCES 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14) 15) 16)
Good, P e a s l e e and D e u t s c h , Phys. Rev. 69 (1946) 313. Ticho, G r e e n and R i c h a r d s o n , Phys. Rev. 86 (1952) 422. R o g g e n k a m p , P r u e t t and W i l k i n s o n , Phys. Rev. 88 (1952) 1262. S t e r k , W a p s t r a and K r o p v e l d , Physica 19 (1953) 135. Casson, G o o d m a n and K r o h n , Phys. Rev. 92 (1953) 1517. V a n Nooijen, Konijn, H e y l i g e r s , V. D. B r u g g e and W a p s t r a , Physica 23 (1957) 753. V a n L i e s h o u t , G r e e n b e r g , K o e r t s and Wu, Phys. Rev. 100 (1955) 223. H a g e d o o r n , H. L. and Konijn, J., Physica 23 {1957} 1069. Zweifel, P. F., Phys. Rev. 107 (1957) 329. Rose, M. E. and J a c k s o n , J. L., Phys. Rev. 76 (1949) 1540. W a p s t r a , Nijgh and Van L i e s h o u t , ,,Nuclear Spectroscopy Tables" North Holland Publishing Company, Amsterdam. In preparation. S h e r r , R. and Miller, R. H., Phys. Rev. 93 (1954) 1076. D r e v e r , M o l j k and Scobie, Phil. Mag. I (1956) 942. Konijn, H a g e d o o r n , V a n Nooijen and W a p s t r a , Nucl. Phys., to be published. S h e l i n e , R. K., Nucl. Phys. 2 (1956) 382. B o e h m , F. and W a p s t r a , A. H., Phys. Rev., to be published.