- Email: [email protected]
Establishment of an excited state at 1.64 keV in 193Pt
Volume 26B, n u m b e r 2
PHYSICS
ESTABLISHMENT
OF
AN
A. J O H A N S S O N , G. M A L M S T E N ,
LETTERS
EXCITED
A. M A R E L I U S ,
25 D e c e m b e r 1967
STATE
AT
1.64
keV
IN
193pt
B. NYMAN, H. P E T T E R S S O N a n d B . S V A H N
Institute of Physics. University of Uppsala. Uppsala, Sweden. Received 21 November 1967
A nuclear energy level of 1.64 keV in 193pt has been established in a high-resolution study of the internal conversion s p e c t r u m in the 193Au decay. The m e a s u r e d half-life is 9.7 i 0.6 ns and the de-exciting t r a n sition is most probably of M1 c h a r a c t e r .
193Au (17.5 h) d e c a y s by e l e c t r o n c a p t u r e to 1 9 3 p t . T h e m o s t e x t e n s i v e i n v e s t i g a t i o n of t h i s d e c a y i s t h a t of E w a n [1], who p r o p o s e d a l e v e l scheme for 193pt, which also fits essentially t h e r e s u l t s of o t h e r i n v e s t i g a t i o n s [2] i n t h e 193Au d e c a y . In t h e p r e s e n t s t u d y i t w a s f o u n d , h o w e v e r , t h a t t h i s l e v e l s c h e m e h a s to b e m o d i fied, the most striking feature being the inclusion of a n e w l e v e l a t 1.64 k e V . T h e i n t e r n a l c o n v e r s i o n s p e c t r u m f r o m 10 to 700 k e V w a s m e a s u r e d w i t h t w o d i f f e r e n t t y p e s of d o u b l e - f o c u s s i n g s p e c t r o m e t e r s [3,4] a n d t e n not previously reported transitions were found. The first evidence for a low-energy level was r e v e a l e d by t h e f a c t t h a t s e v e r a l of t h e s t r o n g e s t t r a n s i t i o n s w e r e f o u n d to a p p e a r in t h e f o r m of c l o s e d o u b l e t s , s p a c e d a b o u t 1.65 k e V ( s e e t a b l e 1). F o r a 1.65 k e V t r a n s i t i o n , i n t e r n a l c o n v e r s i o n i s p o s s i b l e in t h e p l a t i n u m N, O a n d P s h e l l s only, and this energy region was measured with t h e i r o n - f r e e s p e c t r o m e t e r [4], p r o v i d e d w i t h a Mullard electron channel multiplier detector. Table 1 E n e r g i e s of the doublets and the energy differences between t h e i r m e m b e r s . Transition energy (keV) High energy Low energy member member
114.16 ± 0.02
Energy
difference (keV)
112.52 ± 0.02
1.64
119.64 ± 0.03
117.99 ± 0.02
1.65
187.83 ± 0.04
186.16 • 0.02
1.67
269.84 ± 0.05
268.22 ± 0.05
1.62
439.04 ± 0.08
437.41 :L 0.08
1.63
491.28 =L0.12
489.61 ± 0.12
1.67
Electron energy (keY)
__.
o,8o
1 oo
120
i~O~pL
1.64 N, 1.64 N~
~ooo
1.so
1.640,
-
1000
zoo
\
discrete energy losses
1.20
1.40 1 0 Spectrometer current (A)
1.80
2.00
Fig. 1. N and O conversion lines of the 1.64 keV t r a n sition and part of the MXY Auger s p e c t r u m in platinum. T h e e x i s t e n c e of t h e 1.64 keY t r a n s i t i o n i s c l e a r l y v e r i f i e d by t h e p r e s e n c e of t h e w e l l d e f i n e d N1, N 2 a n d O 1 c o n v e r s i o n l i n e s i m p o s e d u p o n a n u n r e s o l v e d b a c k g r o u n d of MXY A u g e r l i n e s in P t (fig. 1). T h e b e s t f i t t e d v a l u e of t h e t r a n s i t i o n e n e r g y i s 1.644 :~ 0 . 0 0 4 k e V i n a g r e e m e n t w i t h t h e s p a c i n g b e t w e e n t h e m e m b e r s of the doublets. T h e h a l f - l i f e of t h e 1.64 k e V l e v e l w a s m e a s u r e d by m e a n s of d e l a y e d c o i n c i d e n c e s . T h e e l e c t r o n - e l e c t r o n s p e c t r o m e t e r [5] u s e d , w a s o p e r a t e d w i t h a p r e a c c e l e r a t i n g v o l t a g e [6] of a b o u t 20 kV. T h e t i m e d i s t r i b u t i o n of c o i n c i d e n c e s b e t w e e n t h e i n t e n s e 186 K l i n e a n d t h e 1.64 N l i n e s w a s m e a s u r e d . A t y p i c a l r e s u l t i s 83
Volume 26B. n u m b e r 2
PHYSICS
LETTERS
25 December 1967 491.25 *- 0.05
Oo oo
52 439.05 ± 0.06
•°
LL O
Z
103
r
•
"*° °%%%TI/2°= 97 ns
•
ADMIXTURE -FROM AUGER ELECTRONS
~sPt;,s
193
1
o
"°#°, ~'~
269.85 -+0.04
3
187.81 ± 0.03
,o~
'
5'o ~ C.ANNEL NUM~E~
1~
"
'7
Fig. 2. Delayed coincidence c u r v e for the 186-1.64 keV cascade. s h o w n in fig. 2. T h e r e a r e c o n t r i b u t i o n s of prompt coincidences from MXY Auger electrons a c c e p t e d i n t h e low e n e r g y c h a n n e l a n d c o i n c i d e n c e s d e l a y e d by t h e h a l f - l i f e [1] of t h e 14.3 k e V level, but also a well-defined exponential distrib u t i o n i n d i c a t i n g a l o n g e r h a l f - l i f e . A n a l y s i s of t h i s s l o p e g i v e s a h a l f - l i f e of 9.7 ± 0.6 n s w h i c h i s a s s i g n e d to t h e 1.64 k e V l e v e l . From L subshell conversion intensity ratios t h e 113 a n d 114 k e V t r a n s i t i o n s a r e b o t h f o u n d to b e of M1 + E 2 c h a r a c t e r a n d c o n s e q u e n t l y t h e m u l t i p o l a r i t y of t h e 1.64 keV t r a n s i t i o n m u s t b e parity-conserving. The measured half-life compared with the conversion corrected Weisskopf h a l f - l i f e e s t i m a t e s [7] i n d i c a t e s t h a t t h e t r a n s i t i o n i s m a i n l y of d i p o l e c h a r a c t e r . C o n s e q u e n t l y t h e m u l t i p o l a r i t y of t h e 1.64 k e V t r a n s i t i o n m u s t b e p r e d o m i n a n t l y M1. The modified 193pt level scheme is shown in fig. 3. T h e p o s s i b l e l e v e l a t 1 1 9 . 6 4 k e V ( c o m p a r e t a b l e 1) i s n o t i n c l u d e d s i n c e t h i s w o u l d b e i n d i s a g r e e m e n t w i t h t h e r e s u l t s of E w a n [1], w h o f o u n d t h e 113 a n d 120 k e V t r a n s i t i o n s to b e c o i n cident. A m o r e d e t a i l e d r e p o r t on t h e 193Au d e c a y will be published elsewhere. We wish to thank Professor Kai Siegbahn for providing excellent working facilities. The ski-
84
74
Ii ,i ]
I
17'4
2:i:i
lo'o 1,LIL/,2 +5
T, 1 I!
I14.16-+0.03
14.20-+o.ol
:,+ooo
Fig, 3. Basic level scheme of 193pt a r r i v e d at in the p r e s e n t study of the 193Au decay. Only quite u n a m b i guously defined levels a r e included. The relative e r r o r s in the energy d e t e r m i n a t i o n s of the t r a n s i t i o n s involved a r e a few p a r t s in 104 except for the 1.64 keV transition. ful a s s i s t a n c e of M r . S. N o r r b y i n p r e p a r i n g t h e sources is greatly appreciated.
References 1. G . T . Ewan, Can. J. Phys. 35 (1957) 672. 2. Nuclear Data Sheets, National Academy of Sciences, National R e s e a r c h Council, Washington D.C. 3. H. P e t t e r s s o n , Y. Grunditz, G. B/~ckstr(~m, O. B e r g man, S.Antman and E . A a s a , Arkiv f. Fysik 29 (1965) 61. 4. K. Siegbahn, C. Nordling, S.E. Karlsson, S. Hags t r u m , A. Fahlman and I . A n d e r s s o n , Nucl. Instr. and Meth. 27 (1964) 173. 5. T . R . G e r h o l m and J . L i n d s k o g , Arkiv f. Fysik 24 (1963) 171. 6. P. S p a r r m a n , J. Lindskog and A. Marelius, Nucl. Instr. and Meth. 41 (1966) 299. 7. A. H. Wapstra, G . J . Nijgh and R. van Lieshout, Nuc l e a r spectroscopy tables (North-Holland Publ. Co., A m s t e r d a m , 1959) chapt. 6.
PHYSICS
ESTABLISHMENT
OF
AN
A. J O H A N S S O N , G. M A L M S T E N ,
LETTERS
EXCITED
A. M A R E L I U S ,
25 D e c e m b e r 1967
STATE
AT
1.64
keV
IN
193pt
B. NYMAN, H. P E T T E R S S O N a n d B . S V A H N
Institute of Physics. University of Uppsala. Uppsala, Sweden. Received 21 November 1967
A nuclear energy level of 1.64 keV in 193pt has been established in a high-resolution study of the internal conversion s p e c t r u m in the 193Au decay. The m e a s u r e d half-life is 9.7 i 0.6 ns and the de-exciting t r a n sition is most probably of M1 c h a r a c t e r .
193Au (17.5 h) d e c a y s by e l e c t r o n c a p t u r e to 1 9 3 p t . T h e m o s t e x t e n s i v e i n v e s t i g a t i o n of t h i s d e c a y i s t h a t of E w a n [1], who p r o p o s e d a l e v e l scheme for 193pt, which also fits essentially t h e r e s u l t s of o t h e r i n v e s t i g a t i o n s [2] i n t h e 193Au d e c a y . In t h e p r e s e n t s t u d y i t w a s f o u n d , h o w e v e r , t h a t t h i s l e v e l s c h e m e h a s to b e m o d i fied, the most striking feature being the inclusion of a n e w l e v e l a t 1.64 k e V . T h e i n t e r n a l c o n v e r s i o n s p e c t r u m f r o m 10 to 700 k e V w a s m e a s u r e d w i t h t w o d i f f e r e n t t y p e s of d o u b l e - f o c u s s i n g s p e c t r o m e t e r s [3,4] a n d t e n not previously reported transitions were found. The first evidence for a low-energy level was r e v e a l e d by t h e f a c t t h a t s e v e r a l of t h e s t r o n g e s t t r a n s i t i o n s w e r e f o u n d to a p p e a r in t h e f o r m of c l o s e d o u b l e t s , s p a c e d a b o u t 1.65 k e V ( s e e t a b l e 1). F o r a 1.65 k e V t r a n s i t i o n , i n t e r n a l c o n v e r s i o n i s p o s s i b l e in t h e p l a t i n u m N, O a n d P s h e l l s only, and this energy region was measured with t h e i r o n - f r e e s p e c t r o m e t e r [4], p r o v i d e d w i t h a Mullard electron channel multiplier detector. Table 1 E n e r g i e s of the doublets and the energy differences between t h e i r m e m b e r s . Transition energy (keV) High energy Low energy member member
114.16 ± 0.02
Energy
difference (keV)
112.52 ± 0.02
1.64
119.64 ± 0.03
117.99 ± 0.02
1.65
187.83 ± 0.04
186.16 • 0.02
1.67
269.84 ± 0.05
268.22 ± 0.05
1.62
439.04 ± 0.08
437.41 :L 0.08
1.63
491.28 =L0.12
489.61 ± 0.12
1.67
Electron energy (keY)
__.
o,8o
1 oo
120
i~O~pL
1.64 N, 1.64 N~
~ooo
1.so
1.640,
-
1000
zoo
\
discrete energy losses
1.20
1.40 1 0 Spectrometer current (A)
1.80
2.00
Fig. 1. N and O conversion lines of the 1.64 keV t r a n sition and part of the MXY Auger s p e c t r u m in platinum. T h e e x i s t e n c e of t h e 1.64 keY t r a n s i t i o n i s c l e a r l y v e r i f i e d by t h e p r e s e n c e of t h e w e l l d e f i n e d N1, N 2 a n d O 1 c o n v e r s i o n l i n e s i m p o s e d u p o n a n u n r e s o l v e d b a c k g r o u n d of MXY A u g e r l i n e s in P t (fig. 1). T h e b e s t f i t t e d v a l u e of t h e t r a n s i t i o n e n e r g y i s 1.644 :~ 0 . 0 0 4 k e V i n a g r e e m e n t w i t h t h e s p a c i n g b e t w e e n t h e m e m b e r s of the doublets. T h e h a l f - l i f e of t h e 1.64 k e V l e v e l w a s m e a s u r e d by m e a n s of d e l a y e d c o i n c i d e n c e s . T h e e l e c t r o n - e l e c t r o n s p e c t r o m e t e r [5] u s e d , w a s o p e r a t e d w i t h a p r e a c c e l e r a t i n g v o l t a g e [6] of a b o u t 20 kV. T h e t i m e d i s t r i b u t i o n of c o i n c i d e n c e s b e t w e e n t h e i n t e n s e 186 K l i n e a n d t h e 1.64 N l i n e s w a s m e a s u r e d . A t y p i c a l r e s u l t i s 83
Volume 26B. n u m b e r 2
PHYSICS
LETTERS
25 December 1967 491.25 *- 0.05
Oo oo
52 439.05 ± 0.06
•°
LL O
Z
103
r
•
"*° °%%%TI/2°= 97 ns
•
ADMIXTURE -FROM AUGER ELECTRONS
~sPt;,s
193
1
o
"°#°, ~'~
269.85 -+0.04
3
187.81 ± 0.03
,o~
'
5'o ~ C.ANNEL NUM~E~
1~
"
'7
Fig. 2. Delayed coincidence c u r v e for the 186-1.64 keV cascade. s h o w n in fig. 2. T h e r e a r e c o n t r i b u t i o n s of prompt coincidences from MXY Auger electrons a c c e p t e d i n t h e low e n e r g y c h a n n e l a n d c o i n c i d e n c e s d e l a y e d by t h e h a l f - l i f e [1] of t h e 14.3 k e V level, but also a well-defined exponential distrib u t i o n i n d i c a t i n g a l o n g e r h a l f - l i f e . A n a l y s i s of t h i s s l o p e g i v e s a h a l f - l i f e of 9.7 ± 0.6 n s w h i c h i s a s s i g n e d to t h e 1.64 k e V l e v e l . From L subshell conversion intensity ratios t h e 113 a n d 114 k e V t r a n s i t i o n s a r e b o t h f o u n d to b e of M1 + E 2 c h a r a c t e r a n d c o n s e q u e n t l y t h e m u l t i p o l a r i t y of t h e 1.64 keV t r a n s i t i o n m u s t b e parity-conserving. The measured half-life compared with the conversion corrected Weisskopf h a l f - l i f e e s t i m a t e s [7] i n d i c a t e s t h a t t h e t r a n s i t i o n i s m a i n l y of d i p o l e c h a r a c t e r . C o n s e q u e n t l y t h e m u l t i p o l a r i t y of t h e 1.64 k e V t r a n s i t i o n m u s t b e p r e d o m i n a n t l y M1. The modified 193pt level scheme is shown in fig. 3. T h e p o s s i b l e l e v e l a t 1 1 9 . 6 4 k e V ( c o m p a r e t a b l e 1) i s n o t i n c l u d e d s i n c e t h i s w o u l d b e i n d i s a g r e e m e n t w i t h t h e r e s u l t s of E w a n [1], w h o f o u n d t h e 113 a n d 120 k e V t r a n s i t i o n s to b e c o i n cident. A m o r e d e t a i l e d r e p o r t on t h e 193Au d e c a y will be published elsewhere. We wish to thank Professor Kai Siegbahn for providing excellent working facilities. The ski-
84
74
Ii ,i ]
I
17'4
2:i:i
lo'o 1,LIL/,2 +5
T, 1 I!
I14.16-+0.03
14.20-+o.ol
:,+ooo
Fig, 3. Basic level scheme of 193pt a r r i v e d at in the p r e s e n t study of the 193Au decay. Only quite u n a m b i guously defined levels a r e included. The relative e r r o r s in the energy d e t e r m i n a t i o n s of the t r a n s i t i o n s involved a r e a few p a r t s in 104 except for the 1.64 keV transition. ful a s s i s t a n c e of M r . S. N o r r b y i n p r e p a r i n g t h e sources is greatly appreciated.
References 1. G . T . Ewan, Can. J. Phys. 35 (1957) 672. 2. Nuclear Data Sheets, National Academy of Sciences, National R e s e a r c h Council, Washington D.C. 3. H. P e t t e r s s o n , Y. Grunditz, G. B/~ckstr(~m, O. B e r g man, S.Antman and E . A a s a , Arkiv f. Fysik 29 (1965) 61. 4. K. Siegbahn, C. Nordling, S.E. Karlsson, S. Hags t r u m , A. Fahlman and I . A n d e r s s o n , Nucl. Instr. and Meth. 27 (1964) 173. 5. T . R . G e r h o l m and J . L i n d s k o g , Arkiv f. Fysik 24 (1963) 171. 6. P. S p a r r m a n , J. Lindskog and A. Marelius, Nucl. Instr. and Meth. 41 (1966) 299. 7. A. H. Wapstra, G . J . Nijgh and R. van Lieshout, Nuc l e a r spectroscopy tables (North-Holland Publ. Co., A m s t e r d a m , 1959) chapt. 6.