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CALIBRATION OF THE ISOMER SHIFT OF THE TWO MÖSSBAUER ISOTOPES 127I AND 129I
P. Müller, W. Kündig
To cite this version:
P. Müller, W. Kündig. CALIBRATION OF THE ISOMER SHIFT OF THE TWO MÖSSBAUER ISOTOPES 127I AND 129I. Journal de Physique Colloques, 1980, 41 (C1), pp.C1-125-C1-126.
�10.1051/jphyscol:1980127�. �jpa-00219695�
JOURNAL DE PHYSIQUE Colloque C1, supplkment au
n
O 1, Tome 41,janvier
1980, pageCl-125
CALIBRATION OF THE ISOMER SHItT OF THE
THO&SBAUER ISOTOPES 1271 AND
112' P.E. Miiller and W. ~ G n d i g1. Introduction.- The Mijssbauer isomer s h i f t 6 be- g e t s f o r t h e measured difference current
tween a p a i r of chemica_l compounds i s given by A1(t) = I-- I+ = (AI(o)
-
1(0)AXt)exp(-At). 18) 6 5 - 5 - 4 a ~ e 2 R AA hp =c
AP, ( 1 ) Thus t h e difference current corrected f o r t h e decay where A p i s t h e difference of t h e e l e c t r o n d e n s i t i e s A1(t)exp(Xt) w i l l increase l i n e a r l y with time with a t t h e nucleus f o r t h e two chemical s t a t e s , and C i s a slope proportional t o AX.t h e "calibration constant" which depends on B, t h e change of t h e nuclear radius during t h e y-transition.
A n experiment t o determine absolute values of Apbased on t h e influence of t h e chemical environ- ment on t h e l i f e t i m e of t h e electron capture decay i n 1 2 5 ~ i s described. From a c o r r e l a t i o n of t h e l i f e time measurements with t h e corresponding Miissbauer isomer s h i f t data, t h e c a l i b r a t i o n constants C ( o r
B ) f o r 1 2 7 ~ and 12', were determined.
An e a r l y analysis of t h e iodine isomer s h i f t d a t a revealed /1/
( L S / R ) ~ ~ ~ / ( & R / R ) ~ ~ ~ = -0.78 0.05 ( 2 ) For t h e individual values of AR/R only estimates e x i s t /2/.
( ARlR),,,
-
- 3 . 3 ~ 0 - ~ , ( l / ~ ) ~ ~ ~ = +)1.2~10-~ ( 3 ) The decay p r o b a b i l i t y f o r e l e c t r o n capture i sgiven by /3/:
X
"
T-' = const2
pi(Eo-
E ~ ) ~ , ( 4 ) where Eo i s t h e t r a n s i t i o n energy and Ei t h e binding energy of t h e captured electron. For 1 2 5 ~ Eq. ( 4 ) reduces t o(AXI'X),~~ = 1.553 (Ap/p) ( 5 ) where t h e values Eo = 147 keV and Els = 33.2 keV were used. This expression combined with ( 1 ) gives
( AR/R),,g = 0.01166 61z9/ {e2RfZg P(9)125 ( 6 ) The t o t a l electron density a t t h e nucleus was extra- polated from Mallow e t a l . / 4 / t o be 2.65~10 a g 3 . 5 In t h e experiment described here t h e isomer s h i f t values
6129 were taken from t h e l i t e r a t u r e . The correspond- i n g Ah/A values were measured with a d i f f e r e n t i a l ionization chamber.
2. Experimental.- The chamber used i n t h e experiment i s shown i n Fig.1. The currents produced i n t h e two chamber halves a r e
I + ( t )
-
= I+(O) exp(-X+t),- -
( 7 ) with t w o sources of approximately equal strength oneELECTROMETER t
Fig. 1 : Cross-section of t h e l e f t h a l f of t h e ioni- zation chamber. The chamber i s f i l l e d with 1 5 a t m of high p u r i t y argon. The sources a r e exchanged pneu- mat i c a l l y
.
For t h e current measurements t h e v i b r a t i n g reed electrometer CARY 401 was used i n t h e r a t e of charge mode. I n one chamber h a l f a fixed 'source was used
(source SO). The source i n t h e other h a l f was C?;langed every two hours. The measurements were done automa- t i c a l l y over a period df more than 1 y. A l l t h e meas- urements were normalized.with respect t o a l i f e t i m e corrected 241~m standard (T = 458 y).
Y2
Altoghether 6 sources (%5 m C i each) were pre- pared from t h e same ' high p u r i t y , aged, and c a r r i e r f r e e batch of 1 2 5 ~ .
S 0,1,2 : Na3H2106 (reference: 6129 = 0 mm/s) S 3 :KI04 ( 6 = 1 . 5 m m / s )
S 4 : K I O j ( 6 = 5.0 mm/s) ( 9 ) s 5
:csrc14
( 6 = 7 . 4 3 m m / s )The sources containing about 100 mg non-radioactive iodine each, were immobilized by, p r i s s i n g with q u ~ 0 . t ~
, .
powder and then sealed i n t o g l a s s ampoules.
3. ~ e s u l t s
.-
Once a week t h e Ahlh experiment was in- t e r r u p t e d f o r 6 h i n order t o determine t h e absolute source s t r e n g t h of one of t h e sources ( N a 3 ~ 2 ~ ~ 6 ) , see Fig. 2.Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980127
JOURNAL DE PHYSIQUE
t h e various possible difference currents, t h e t o t a l s e t of data was f i t t e d t o
2 0
- 100
TlME [dl
Fig. 2 : Section of t h e 1 2 5 ~ decay curve. The errozs of t h e experimental points a r e approximately a fac- t o r 10 smaller than t h e poirlts sbown.
The half l i f e of 1251 determined by a weighted f i t Of t h e data points was found t o be
T~ = 59.666 5 0.016 d
.
(10)a value which may be compared with t h e present a v e r age of Ty2 = 60.14 f 0.11 d given i n t h e Nucl. Data Sheets.
Examples of t h e AX/X measurements a r e shown i n Fig.3. The observed deviation from t h i s l i n e a r re- l a t i o n must be explained by source i n s t a b i l i t i e s . It may be assumed t h a t t h e deviations show an expo- nential behaviour.
I I I I I I
I I00 200 300
TlME [DAYS]
Fig. 3 : Lifetime corrected current of t h e diffe- r e n t i a l ionization chamber plotted. a s a function of time. The three sources were measured r e l a t i v e t o a Na3H2106 source.
The calculated l i n e a r slopes a r e only approximately proportional t o t h e corresponding isomer s h i f t s . In order t o account f o r t h e known correlations between
For t h i s f i t 11 independent parameters a r e required.
The f i t t e d exponential factor was assumed t o be t h e same for a l l t h e sources. The r e s u l t i s
( A X / X ) ~ ~ ~ = (1.22 k 0.08) x 10-5 x 6129 (mm/s).
The r e s u l t from t h e individual difference currents (Fig. 3) i s
( 8 ~ 1= ~(1.68 ) ~f 0.20) ~ ~ x 10-5 x 6129 (mmls) with an estimated average of (1.55
+
0.35) x 10-5one gets using Eq. 6 with R124 = 6.12
a:
( A R / R ) ~ ~ ~ =
+
(7.2 f 1.7) x 10-4.The e r r o r i s increased by a factor or aDouz r In order t o account f o r various inconsistencies. This value i s approximately a f a c t o r two higher than e a r l i e r estimates ( 3 ) .
TlME [DAY]
Fig. 4 : Lifetime corrected current f o r a l l combin- ations of t h e sources S 1,2,4, and 5. The v e r t i c a l scale f o r t h e various curves i s a r b i t r a r i l y shifted.
The l i n e s p l o t t e d a r e from one general f i t t o Eq.Y.
The r e l a t i v e isomer s h i f t s a r e indicated, they a r e proportional t o t h e slope of t h e curves given.
The authors would l i k e t o thank D r . B. Sawicka f o r her help i n t h e e a r l y phase of t h i s experiment.
References
/1/ S.L. Ruby and G.K. Shenoy, Phys. Rev.
186, 326 (1969).
-
/2/ G.M. Kalvius and G.K. Shenoy, Atomic Data and Nucl. Data Tables
&,
639 (1974)./3/ K. Alder, J. Hadermann, and U. Raff, Phys. Lett.
30,
487 (1969)./4/ J.V. Mallow, A.J. Freeman, and J.P. Des- claux, Phys. Rev.
