HAL Id: jpa-00219698

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HAL Id: jpa-00219698

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Submitted on 1 Jan 1980

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ISOMER SHIFT CALIBRATION OF 129I AND 127I BY LIFE-TIME VARIATIONS IN THE

ELECTRON-CAPTURE DECAY OF 123I

J. Ladrière, M. Cogneau, A. Meykens

To cite this version:

J. Ladrière, M. Cogneau, A. Meykens. ISOMER SHIFT CALIBRATION OF 129I AND 127I BY

LIFE-TIME VARIATIONS IN THE ELECTRON-CAPTURE DECAY OF 123I. Journal de Physique

Colloques, 1980, 41 (C1), pp.C1-131-C1-132. �10.1051/jphyscol:1980130�. �jpa-00219698�

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JOURNAL DE PHYSIQUE Colloque Cl, supplbment au

no

1, Tome 41, janvier 1980, page C1-131

J. Ladrigre, M. Cogneau and A. Meykens

+

Luboratoire de C h i d e I n o r g k q u e e t NucZdaire, Universitd de Louvain, Louvain-la-Neuve, B e Z g h .

+

I n s t i t u u t voor Kern- en StraZingsfysika, Universiteit t e Leuven, Belgium.

1. I n t r o d u c t i o n . - I n o r d e r t o c a l i b r a t e t h e isomer s h i f t 6 of a Massbauer i s o t o p e

2 ~ ~ e 2 c 2

GCm.s-l) =

-

A<r >Ap = a.Ap

,

3EY

it i s n e c e s s a r y t o e v a l u a t e c a r e f u l l y t h e e l e c t r o n d e n s i t y d i f f e r e n c e s Ap a t t h e n u c l e u s .

I n a p r e v i o u s work / I / , t h e c a l i b r a - t i o n o f t h e 5 7 ~ e isomer s h i f t h a s been d e t e r m i n e d u s i n g e x p e r i m e n t a l , A D - v a l u e s o b t a i n e d from measurements o f t h e v a r i a - t i o n s i n t h e e l e c t r o n - c a p t u r e ( E . C . ) decay r a t e i n v a r i o u s 5 2 ~ e l a b e l l e d compounds.

Such e x p e r i m e n t s u s e t h e p r o p o r t i o n a l i t y o f t h i s decay-mode c o n s t a n t X t o t h e e l e c t r o n d e n s i t y a t t h e n u c l e u s p . By comparing two c h e m i c a l l y d i f f e r e n t compounds, t h e r e l a t i v e v a r i a t i o n o f t h e

A X

decay c o n s t a n t ,

-,

A i s t h e r e f o r e r e l a t e d t o A P by t h e f o l l o w i n g e x p r e s s i o n :

x

= k&.

X P

where k = 1, i f exchange and o v e r l a p e f - f e c t s / 2 / are n e g l e c t e d .

T h i s s t u d y can be e x t e n d e d t o o t h e r e l e m e n t s h a v i n g b o t h Massbauer and E . C . d e c a y i n g i s o t o p e s . One o f t h e most a p p r o - p r i a t e s y s t e m s i s 1 2 7 - 1 2 9 ~ and 1 2 3 ~

(100 % E.C., X

=

1.447 s - I ) , which can be compared, f o r i s o e l e c t r o n i c compounds, t o o t h e r systems l i k e 1 2 5 ~ e

-

' l 9 ~ e and 129-13Ixe

-

^122xe.

I n i o d i n e compounds e l e c t r o n d e n s i t i e s a t t h e n u c l e u s f o r v a r i o u s e l e c t r o n i c con- f i g u r a t i o n s have been w e l l e s t a b l i s h e d u s i n g D i r a c - S l a t e r c a l c u l a t i o n s /3/.

However, d i f f e r e n t A<r 2 > - v a l u e s a r e found i n t h e l i t e r a t u r e (A<r >129 2 =

%/,

1 8 . 5 / 5 / and 2 1 / 6 / . 1 0 - ~ fm 2 and i t seemed i n t e r e s t i n g t o make an e x p e r i m e n t a l e s t i - m a t i o n of t h i s p a r a m e t e r .

2 . E x p e r i m e n t a l . - D i r e c t measurements o f A X f o r s e v e r a l p a i r s o f i o d i n e compounds l a b e l l e d w i t h 1 2 3 ~ have been performed u s i n g d i f f e r e n t i a l i o n i z a t i o n c h a m b e r s / l /

.

The i n i t i a l a c t i v i t i e s i n t r o d u c e d i n t o t h e two chambers have been a d j u s t e d t o t h e same v a l u e ( 1 0

2

m C i ) by w e i g h ~ i n g s t o e c h i o m e t r i c e q u i v a l e n t q u a n t i t i e s o f t h e two compounds. For e a c h p a i r o f s o u r c e s two measurements a r e made by i n t e r c h a n g i n g t h e s o u r c e s from one cham- b e r t o t h e o t h e r , s o t h a t t h e i r a r i t h m e t i c mean c a n c e l s t h e z e r o e f f e c t o f t h e appa- r a t u s .

The 1 2 3 ~ a c t i v i t y i s produced by t h e n u c l e a r p r o c e s s e s

a t a p r o t o n e n e r g y o f 65 MeV. The r a d i o - n u c l i d i c p u r i t y i s v e r y h i g h ; o n l y

1 2 5 I ( T l I 2 = 60 d ) i s d e t e c t a b l e w i t h a maximum o f 0.2 % and i t d o e s n o t p e r t u r b o u r measurements owing t o i t s l o n g h a l f - l i f e .

I n t h i s work, two l i f e - t i m e v a r i a t i o n measurements have been made by comparing, a t room t e m p e r a t u r e , KI04 and Na3H2106 t o KI03. The isomer s h i f t s o f t h e 1 2 9 ~ , c o r - r e s p o n d i n g compounds a r e t a k e n from t h e l i t e r a t u r e :

compound TK6zn129Te(mm.s'1) r e f .

KI03 80

+

1 . 5 6 ( 2 0 ) / 7 /

KI04 80

-

^2.34 ⁽⁶⁾ / 7/

Na3H2106 20

-

3.35 ( 2 ) / 8 /

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980130

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C1-132 JOURNAL DE PHYSIQUE

3. R e s u l t s and d i s c u s s i o n .

-

The r e s u l t s a r e summarized i n t a b l e 1. The e r r o r s on

A X a r e p u r e s t a t i s t i c a l . I n d i c e s + and

-

r e f e r t o t h e p o l a r i t y o f t h e i o n i z a t i o n chambers. The r e l a t i v e change i n t h e de- c a y c o n s t a n t i s t h e f i t t e d ( X -

-

^{A + )} v a l u e , d i v i d e d by h = 1.447 s - l . It i s s e e n from t h e s e r e s u l t s t h a t no i m p o r t a n t asymmetry o f t h e two chambers a p p e a r s w h i l e r e v e r - s i n g t h e s o u r c e s and t h a t t h e s i g n o f ( A -

-

A+) r e v e r s e s t o o .

F i g u r e 1 shows t h e dependence o f Ah i n 1 2 3 ~ compounds v e r s u s t h e isomer s h i f t d i f f e r e n c e s f o r t h e 1 2 9 ~ c o r r e s p o n d i n g compounds.

TABLE 1

F i g u r e 1

p a i r s o f 1 2 3 ~ s o u r c e s

+ ^-

mm. s ^-1

- -

a

-

3

0

( a ) 12'1 isomer s h i f t

( b ) a r i t h m e t i c mean o f symmetric e x p e r i m e n t s , f o r A 6 p o s i t i v e .

Using t h e r e l a t i v i s t i c v a l u e o f 2 6

P = 241,235 a i 3 ( 5 s 5p ) 3 we a r e a b l e t o d e t e r m i n e ( f o r k = 1) t h e c a l i b r a t i o n c o n s t a n t a and A+ 2 >, t h e change i n t h e mean s q u a r e c h a r g e r a d i u s o f t h e ^{1 2 g I}

+

3

n u c l e u s : a129 =+0.20-0.03 a . m . s - '

0

2 2

A<r > _{1 2 9;}+ ( 1 8 ' 3 ) 1 0 - ~ f m

.

2 2

Taking A<r >127/A<r >129 = - 0 . 6 5 / 9 / , t h o s e p a r a m e t e r s c a n a l s o be e v a l u a t e d f o r t h e 1 2 7 ~ n u c l e u s :

a12? = - ( 0 . 0 6 ~ 0 . 0 1 ) d o . 3 m m . s

-

¹

2 2

A<P = - ( 1 2 + 2 ) 1 0 - ~ . f m

.

Acknowledgements.- The a u t h o r s wish t o t h a n k t h e s t a f f o f t h e cyclo.tron of Louvain- la-Neuve f o r t h e p r o d u c t i o n o f 1 2 3 ~ a c t i - v i t y . The f i n a n c i a l s u p p o r t o f t h e I . I . S . N .

-

I . I . K . W . i s g r e a t l y acknowledged.

R e f e r e n c e s

/1/ L a d r i S r e ,J., Meykens ,A. and a l . , J.

Physique

40

(1979)C2-20.

/ 2 / B a h ~ a l 1 , J . N . ~ Phys. Rev. G ( 1 9 6 3 1 3 6 2 . / 3 / Ruby,S.L. and Shenoy,G.K. , i n MSssbauer Isomer S h i f t

,

Shenoy ^{y G .}K. ,Wagner ,F. E.

,

North-Holland (1978) p.623.

/ 4 / , / 5 / i b i d e m / 3 / p. 621, p. 871.

/ 6 / De Waard,H., i n MGssbauer E f f e c t Data I n d e x , Stevens,J.G. and Stevens,V.E., H i l g e r , A . , ( I 9 7 3 1 p 447.

/ 7 / Hafemeister,D.W.

,

De P a s q u a l i , G . and D e Waard,H., Phys. Rev. 135(1964)B1089.

/ 8 / Rama Reddy,K., De Soussa B a r r o s , F . , De B e n e d e t t i , S . , Phys. L e t . a ( 1 9 6 6 ) 2 9 7 . / 9 / Greenw00d~N.N. and Gibb,T.C., MGssbauer

S p e c t r o s c o p y , Chapman H a l l (1971) p 465.

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