ISOMER SHIFT CALIBRATION OF 129I AND 127I BY LIFE-TIME VARIATIONS IN THE ELECTRON-CAPTURE DECAY OF 123I

(1)

HAL Id: jpa-00219698

https://hal.archives-ouvertes.fr/jpa-00219698

Submitted on 1 Jan 1980

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

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�

(2)

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

(3)

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