- Email: [email protected]
The decay of 193 Osmium
De W a a r d , H. 1954
Physica XX 41-43
LETTER The
decay
TO THE
EDITOR
of 193 Osmium
R e c e n t r e p o r t s o n t h e r a d i a t i o n s o c c u r r i n g in t h e 32 h o u r d e c a y of 193 O s m i u m *) l e a v e c o n s i d e r a b l e u n c e r t a i n t y a b o u t its d e c a y s c h e m e . W h i l e B u n k e r e t al. 1) c o n c l u d e t h a t t h e r e is n o 7 - r a d i a t i o n f o l l o w i n g t h e 32 h o u r E-decay, M c G ow a n 3) m e a s u r e d a n i s o m e r i c s t a t e a t 65 k e V w i t h a h a l f life of 5.7 x 10 - 9 sec in 193 i r i d i u m . L a t e r S w a n n a n d H i 11 3) f o u n d w e a k c o n v e r s i o n lines w i t h h a l f lives c o n s i s t e n t w i t h a 32 h o u r d e c a y t h a t i n d i c a t e t h e p r e s e n c e of 7-lines a t 72.4, 215, 323 a n d 460 keV. F i n a l l y C o r k e t al. 4) e v e n f o u n d 9 7-rays, t h e e x i s t e n c e of w h i c h is c o n c l u d e d f r o m 18 c o n v e r s i o n lines f o u n d w i t h a m a g n e t i c - p h o t o g r a p h i c s p e c t r o m e t e r of h i g h r e s o l v i n g power. A n a t t e m p t w a s m a d e t o e s t a b l i s h t h e d i s i n t e g r a t i o n s c h e m e of t h e 193Os d e c a y w i t h t h e aid of a n e l e c t r o n c o i n c i d e n c e s p e c t r o m e t e r . T h i s i n s t r u m e n t c o m p r i s e s a m a g n e t i c lens s p e c t r o m e t e r w i t h a n a n t h r a c e n e c r y s t a l as t h e d e t e c t o r a n d a 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 e q u i p p e d w i t h a n o t h e r a n t h r a c e n e c r y s t a l n e a r t h e source. Coincid e n c e s are r e c o r d e d b e t w e e n t h e p u l s e s p r o d u c e d b y t h e c r y s t a l s in E M I 6260 p h o t o m u l t i p l i e r s , t h e d e t e c t o r c r y s t a l a c c e p t i n g t h e c o n v e r s i o n lines of t h e s p e c t r u m a n d t h e 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 r y s t a l t h e E - c o n t i n u u m . A d e t a i l e d a c c o u n t of t h e o p e r a t i o n of t h i s i n s t r u m e n t a n d of t h e e x p e r i m e n t s l e a d i n g t o t h e r e s u l t s s u m m a r i z e d i n t h i s l e t t e r will s h o r t l y b e p u b l i s h e d 5). T a b l e I gives a list of t h e c o n v e r s i o n lines f o u n d in t h e single c o u n t s p e c t r u m r e c o r d e d by.,the m a g n e t i c s p e c t r o m e t e r ( c o l u m n 2) a n d i n t h e " t o t a l " c o i n c i d e n c e s p e c t r u m ( c o l u m n 3), c o m p a r e d w i t h t h e d a t a of C o r k (col. 4) a n d i n t e r p r e t e d in c o l u m n 5. T h e " t o t a l " c o i n c i d e n c e s p e c t r u m w a s o b t a i n e d b y c o u n t i n g c o i n c i d e n c e s b e t w e e n t h e s p e c t r u m a n a l y z e d in t h e m a g n e t i c s p e c t r o m e t e r a n d t h e E - c o n t i n u u m f r o m w h i c h t h e soft c o n v e r s i o n - a n d E - e l e c t r o n s ( < 150 keV) were l a r g e l y a b s o r b e d b y a n Al-foil, p l a c e d b e t w e e n t h e s p e c t r o m e t e r c r y s t a l a n d t h e source. N o n e of t h e c o n v e r s i o n lines a t 30.4, 93.0, 103.1 a n d 105.1. k e V a s c r i b e d b y C o r k t o a 106.3 k e V t r a n s i t i o n c o u l d b e f o u n d n o r was a c o n v e r sion line a t 328 k e V o b s e r v e d . T h e lines a t 175.2 a n d 481.7 k e V w e r e v e r y w e a k , b o t h in t h e c o i n c i d e n c e a n d t h e single c o u n t s p e c t r u m . O n t h e o t h e r h a n d t h e lines a t 66.5 k e V (M73) a n d a t 447 k e V (L460) w e r e n o t r e p o r t e d b y C o r k . T h e lines in c o l u m n s 2 a n d 3 were n o t c o r r e c t e d for t h e t h i c k hess of t h e s o u r c e ( a b o u t 5 m g / c m 2) a n d t h e r e f o r e s h o w s h i f t s t o l o w e r e n e r g i e s as c o m p a r e d w i t h t h o s e a c c u r a t e l y d e t e r m i n e d b y C o r k. W e a c c e p t e d t h e v a l u e s of t h e ~-energies g i v e n b y C o r k. F r o m a t o t a l c o i n c i d e n c e m e a s u r e m e n t w i t h a v a r i a b l e d e l a y in t h e 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 a h a l f life of (6.0 4- 0.4) x !0 - 9 sec w a s c o n f i r m e d for t h e 73 k e V t r a n s i t i o n . T h e 139 a n d 281 k e V t r a n s i t i o n s were f o u n d t o h a v e h a l f l i v e s ,< 2 X 10 - g s e c . C o i n c i d e n c e s b e t w e e n a p a r t of t h e E - c o n t i n u u m i n c i d e n t o n t h e s c i n t i l l a t i o n *) S w a n n and H i I 1 s) definitely showed that the 32 hr period must be assigned to t93Os instead of 19tOs.
- -
41
- -
42
T H E D E C A Y OF 193OSMIUM TABLE I Conversion lines in the decay of 19aOs and 19tOs
isotope
lines in coineidence s p e c t r u m (keV)
lines in single count spectrum (keV)
19~0s
lines found by C o r k in ~gSOs decay (keV)
interpretation conversion shell
28.0 37.0 50.4 112.0
58.0 59.0 66.5
5810
58.0 66.5
122
I
L
I I
42
I
42
i
129 129
73 139 73
93.0 103.1 105.1 125.2 135,2 175.2 204.7 245.1 267.4
122 134 179 199 240 269
174 2O3 242 269
L M K
30.4 59.7, 60.3 63.1
~gSOs
7-energy (keV)
L M K? K
J
139
139 251 ?
i
I(
L
281 321 281
277.6
312
306
382 443 478
384 447 477
307.5 328.0 384.4
321
K I. K?
481.7
I
460 460
558?
s p e c t r o m e t e r a n d t h e t o p of 5 c o n v e r s i o n l i n e s w e r e d e t e r m i n e d a s a f u n c t i o n of t h e s e t t i n g of t h e d i f f e r e n t i a l d i s c r i m i n a t o r u s e d in c o n j u n c t i o n w i t h t h e s c i n t i l l a t i o n spectrometer. Spectra were thus obtained of the partial fl-decays coincident with the c o n v e r s i o n l i n e s . T a b l e I I ( c o l u m n 2) s u m m a r i z e s t h e d i f f e r e n c e s . I E , , a , . b e t w e e n T A B L E II Energies of fl-compo~aents in coincidence with conversion lines A E m a x of coincident fl-com-
conversion line L73 L139 K28t I(321 1(460
ponent and 1.10 MeV branch ! (keV) I I I I ]
80 ± 145 -;300 i 400-± 450 ±
30 35 50 100 100
Ema x of coincident ~-compo-
nents concluded to exist (keV) 1030 960 820
J"
640
t h e m a x i m u m e n e r g i e s of t h e s e p a r t i a l s p e c t r . a a n d t h e p r e d o m i n a n t f l - c o m p o n e n t w i t h E , n a , = 1.10 M e V , t h a t l e a d s d i r e c t l y t o t h e g r o u n d s t a t e of 193Ir. T h r e e n e w fl-components were thus found. A disintegration scheme was constructed from these data (figure). From the coincidence measurements a preliminary estimate was made of the r e l a t i v e i n t e n s i t i e s of t h e f l - c o m p o n e n t s in c o i n c i d e n c e w i t h c o n v e r s i o n l i n e s . T h e s e
THE DECAY OF 193OSMIUM
43
i n t e n s i t i e s a r e b e l i e v e d t o b e all b e t w e e n 0.05 a n d 0.001 of t h e i n t e n s i t y of t h e .1.10 M e V c o m p o n e n t , so t h a t t h e log ( f t ) - v a l u e s of t h e s e f l - c o m p o n e n t s w o u l d lie b e t w e e n 8.4 a n d 10, w h i c h p u t s t h e m in t h e f i r s t f o r b i d d e n g r o u p .
PN
193 os
~
820 640
321
281
139
d~a
~
~
1931r
Fig. 1. D i s i n t e g r a t i o n s c h e m e of 193Os. All e n e r g i e s are in keV. A s s u m i n g t h e g r o u n d s t a t e of 193Os t o b e p3/.,., spin a n d p a r i t y a s s i g n m e n t s for t h e e x c i t e d 193Ir levels c a n b e g i v e n t h a t a r e c o n s i s t e n t w i t h all e x p e r i m e n t a l d a t a a n d w i t h shell m o d e l e x p e c t a t i o n s . T h e a s s i g n m e n t a p p e a r s t o b e u n a m b i g u o u s o n l y for t h e 73 k e V s t a t e (gT/2) t h a t c e r t a i n l y d e c a y s b y E 2 - r a d i a t i o n . T h i s w o r k f o r m s a p a r t of t h e r e s e a r c h p r o g r a m of t h e " S t i c h t i n g v o o r F u n d a m e n t e e l O n d e r z o e k d e r M a t e r i e " (F.O.M.), f i n a n c i a l l y s u p p o r t e d b y t h e N e t h e r l a n d s O r g a n i z a t i o n for P u r e R e s e a r c h (Z.\V.O.). T h e a u t h o r is i n d e b t e d t o J. G. S i e kin a n a n d P. B o s k m a for t h e i r v a l u a b l e a s s i s t a n c e t h r o u g h o u t t h i s i n v e s t i g a t i o n . H. DE ~'VAARD. Natuurkundig Laboratorium der Rijks-Utliversiteit, (]roniugen, Nederlaud. Received 4-1-54.
REIZI'RF.NCFS 1) 2) 3) 4)
Bunker, M.E., C a n a d a , R. and M i t c h e l l , A.C.G.,Phys. Rev. 7!l(1950) 610. Mc G o w a n, F. K., Phys. Rev. 7t1 (1950) 404 and ORNL-952. S w a r m , J . B . and H i l l , R.D.,Phys. Rev. 88(1952) e31. C o r k , J.M., L e B l a n c , J.M., N e s t e r , W.H., M a r t i n , D.W. and B r i c e , M. K., Phys. Rev. ~}O(1953) 444. 5) D e W a a r d , 'H. and S i e k m a n , J. G., to be published ill Physiea; D e X V a a r d , H., thesis, Groningen 1954..
Physica XX 41-43
LETTER The
decay
TO THE
EDITOR
of 193 Osmium
R e c e n t r e p o r t s o n t h e r a d i a t i o n s o c c u r r i n g in t h e 32 h o u r d e c a y of 193 O s m i u m *) l e a v e c o n s i d e r a b l e u n c e r t a i n t y a b o u t its d e c a y s c h e m e . W h i l e B u n k e r e t al. 1) c o n c l u d e t h a t t h e r e is n o 7 - r a d i a t i o n f o l l o w i n g t h e 32 h o u r E-decay, M c G ow a n 3) m e a s u r e d a n i s o m e r i c s t a t e a t 65 k e V w i t h a h a l f life of 5.7 x 10 - 9 sec in 193 i r i d i u m . L a t e r S w a n n a n d H i 11 3) f o u n d w e a k c o n v e r s i o n lines w i t h h a l f lives c o n s i s t e n t w i t h a 32 h o u r d e c a y t h a t i n d i c a t e t h e p r e s e n c e of 7-lines a t 72.4, 215, 323 a n d 460 keV. F i n a l l y C o r k e t al. 4) e v e n f o u n d 9 7-rays, t h e e x i s t e n c e of w h i c h is c o n c l u d e d f r o m 18 c o n v e r s i o n lines f o u n d w i t h a m a g n e t i c - p h o t o g r a p h i c s p e c t r o m e t e r of h i g h r e s o l v i n g power. A n a t t e m p t w a s m a d e t o e s t a b l i s h t h e d i s i n t e g r a t i o n s c h e m e of t h e 193Os d e c a y w i t h t h e aid of a n e l e c t r o n c o i n c i d e n c e s p e c t r o m e t e r . T h i s i n s t r u m e n t c o m p r i s e s a m a g n e t i c lens s p e c t r o m e t e r w i t h a n a n t h r a c e n e c r y s t a l as t h e d e t e c t o r a n d a 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 e q u i p p e d w i t h a n o t h e r a n t h r a c e n e c r y s t a l n e a r t h e source. Coincid e n c e s are r e c o r d e d b e t w e e n t h e p u l s e s p r o d u c e d b y t h e c r y s t a l s in E M I 6260 p h o t o m u l t i p l i e r s , t h e d e t e c t o r c r y s t a l a c c e p t i n g t h e c o n v e r s i o n lines of t h e s p e c t r u m a n d t h e 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 r y s t a l t h e E - c o n t i n u u m . A d e t a i l e d a c c o u n t of t h e o p e r a t i o n of t h i s i n s t r u m e n t a n d of t h e e x p e r i m e n t s l e a d i n g t o t h e r e s u l t s s u m m a r i z e d i n t h i s l e t t e r will s h o r t l y b e p u b l i s h e d 5). T a b l e I gives a list of t h e c o n v e r s i o n lines f o u n d in t h e single c o u n t s p e c t r u m r e c o r d e d by.,the m a g n e t i c s p e c t r o m e t e r ( c o l u m n 2) a n d i n t h e " t o t a l " c o i n c i d e n c e s p e c t r u m ( c o l u m n 3), c o m p a r e d w i t h t h e d a t a of C o r k (col. 4) a n d i n t e r p r e t e d in c o l u m n 5. T h e " t o t a l " c o i n c i d e n c e s p e c t r u m w a s o b t a i n e d b y c o u n t i n g c o i n c i d e n c e s b e t w e e n t h e s p e c t r u m a n a l y z e d in t h e m a g n e t i c s p e c t r o m e t e r a n d t h e E - c o n t i n u u m f r o m w h i c h t h e soft c o n v e r s i o n - a n d E - e l e c t r o n s ( < 150 keV) were l a r g e l y a b s o r b e d b y a n Al-foil, p l a c e d b e t w e e n t h e s p e c t r o m e t e r c r y s t a l a n d t h e source. N o n e of t h e c o n v e r s i o n lines a t 30.4, 93.0, 103.1 a n d 105.1. k e V a s c r i b e d b y C o r k t o a 106.3 k e V t r a n s i t i o n c o u l d b e f o u n d n o r was a c o n v e r sion line a t 328 k e V o b s e r v e d . T h e lines a t 175.2 a n d 481.7 k e V w e r e v e r y w e a k , b o t h in t h e c o i n c i d e n c e a n d t h e single c o u n t s p e c t r u m . O n t h e o t h e r h a n d t h e lines a t 66.5 k e V (M73) a n d a t 447 k e V (L460) w e r e n o t r e p o r t e d b y C o r k . T h e lines in c o l u m n s 2 a n d 3 were n o t c o r r e c t e d for t h e t h i c k hess of t h e s o u r c e ( a b o u t 5 m g / c m 2) a n d t h e r e f o r e s h o w s h i f t s t o l o w e r e n e r g i e s as c o m p a r e d w i t h t h o s e a c c u r a t e l y d e t e r m i n e d b y C o r k. W e a c c e p t e d t h e v a l u e s of t h e ~-energies g i v e n b y C o r k. F r o m a t o t a l c o i n c i d e n c e m e a s u r e m e n t w i t h a v a r i a b l e d e l a y in t h e 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 a h a l f life of (6.0 4- 0.4) x !0 - 9 sec w a s c o n f i r m e d for t h e 73 k e V t r a n s i t i o n . T h e 139 a n d 281 k e V t r a n s i t i o n s were f o u n d t o h a v e h a l f l i v e s ,< 2 X 10 - g s e c . C o i n c i d e n c e s b e t w e e n a p a r t of t h e E - c o n t i n u u m i n c i d e n t o n t h e s c i n t i l l a t i o n *) S w a n n and H i I 1 s) definitely showed that the 32 hr period must be assigned to t93Os instead of 19tOs.
- -
41
- -
42
T H E D E C A Y OF 193OSMIUM TABLE I Conversion lines in the decay of 19aOs and 19tOs
isotope
lines in coineidence s p e c t r u m (keV)
lines in single count spectrum (keV)
19~0s
lines found by C o r k in ~gSOs decay (keV)
interpretation conversion shell
28.0 37.0 50.4 112.0
58.0 59.0 66.5
5810
58.0 66.5
122
I
L
I I
42
I
42
i
129 129
73 139 73
93.0 103.1 105.1 125.2 135,2 175.2 204.7 245.1 267.4
122 134 179 199 240 269
174 2O3 242 269
L M K
30.4 59.7, 60.3 63.1
~gSOs
7-energy (keV)
L M K? K
J
139
139 251 ?
i
I(
L
281 321 281
277.6
312
306
382 443 478
384 447 477
307.5 328.0 384.4
321
K I. K?
481.7
I
460 460
558?
s p e c t r o m e t e r a n d t h e t o p of 5 c o n v e r s i o n l i n e s w e r e d e t e r m i n e d a s a f u n c t i o n of t h e s e t t i n g of t h e d i f f e r e n t i a l d i s c r i m i n a t o r u s e d in c o n j u n c t i o n w i t h t h e s c i n t i l l a t i o n spectrometer. Spectra were thus obtained of the partial fl-decays coincident with the c o n v e r s i o n l i n e s . T a b l e I I ( c o l u m n 2) s u m m a r i z e s t h e d i f f e r e n c e s . I E , , a , . b e t w e e n T A B L E II Energies of fl-compo~aents in coincidence with conversion lines A E m a x of coincident fl-com-
conversion line L73 L139 K28t I(321 1(460
ponent and 1.10 MeV branch ! (keV) I I I I ]
80 ± 145 -;300 i 400-± 450 ±
30 35 50 100 100
Ema x of coincident ~-compo-
nents concluded to exist (keV) 1030 960 820
J"
640
t h e m a x i m u m e n e r g i e s of t h e s e p a r t i a l s p e c t r . a a n d t h e p r e d o m i n a n t f l - c o m p o n e n t w i t h E , n a , = 1.10 M e V , t h a t l e a d s d i r e c t l y t o t h e g r o u n d s t a t e of 193Ir. T h r e e n e w fl-components were thus found. A disintegration scheme was constructed from these data (figure). From the coincidence measurements a preliminary estimate was made of the r e l a t i v e i n t e n s i t i e s of t h e f l - c o m p o n e n t s in c o i n c i d e n c e w i t h c o n v e r s i o n l i n e s . T h e s e
THE DECAY OF 193OSMIUM
43
i n t e n s i t i e s a r e b e l i e v e d t o b e all b e t w e e n 0.05 a n d 0.001 of t h e i n t e n s i t y of t h e .1.10 M e V c o m p o n e n t , so t h a t t h e log ( f t ) - v a l u e s of t h e s e f l - c o m p o n e n t s w o u l d lie b e t w e e n 8.4 a n d 10, w h i c h p u t s t h e m in t h e f i r s t f o r b i d d e n g r o u p .
PN
193 os
~
820 640
321
281
139
d~a
~
~
1931r
Fig. 1. D i s i n t e g r a t i o n s c h e m e of 193Os. All e n e r g i e s are in keV. A s s u m i n g t h e g r o u n d s t a t e of 193Os t o b e p3/.,., spin a n d p a r i t y a s s i g n m e n t s for t h e e x c i t e d 193Ir levels c a n b e g i v e n t h a t a r e c o n s i s t e n t w i t h all e x p e r i m e n t a l d a t a a n d w i t h shell m o d e l e x p e c t a t i o n s . T h e a s s i g n m e n t a p p e a r s t o b e u n a m b i g u o u s o n l y for t h e 73 k e V s t a t e (gT/2) t h a t c e r t a i n l y d e c a y s b y E 2 - r a d i a t i o n . T h i s w o r k f o r m s a p a r t of t h e r e s e a r c h p r o g r a m of t h e " S t i c h t i n g v o o r F u n d a m e n t e e l O n d e r z o e k d e r M a t e r i e " (F.O.M.), f i n a n c i a l l y s u p p o r t e d b y t h e N e t h e r l a n d s O r g a n i z a t i o n for P u r e R e s e a r c h (Z.\V.O.). T h e a u t h o r is i n d e b t e d t o J. G. S i e kin a n a n d P. B o s k m a for t h e i r v a l u a b l e a s s i s t a n c e t h r o u g h o u t t h i s i n v e s t i g a t i o n . H. DE ~'VAARD. Natuurkundig Laboratorium der Rijks-Utliversiteit, (]roniugen, Nederlaud. Received 4-1-54.
REIZI'RF.NCFS 1) 2) 3) 4)
Bunker, M.E., C a n a d a , R. and M i t c h e l l , A.C.G.,Phys. Rev. 7!l(1950) 610. Mc G o w a n, F. K., Phys. Rev. 7t1 (1950) 404 and ORNL-952. S w a r m , J . B . and H i l l , R.D.,Phys. Rev. 88(1952) e31. C o r k , J.M., L e B l a n c , J.M., N e s t e r , W.H., M a r t i n , D.W. and B r i c e , M. K., Phys. Rev. ~}O(1953) 444. 5) D e W a a r d , 'H. and S i e k m a n , J. G., to be published ill Physiea; D e X V a a r d , H., thesis, Groningen 1954..