COMPLEMENTARY DATA FOR ISOMER SHIFT INTERPRETATION : CHEMICAL CHANGES OF THE HIGHLY CONVERTED HIGH MULTIPOLARITY TRANSITIONS PROBABILITIES

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COMPLEMENTARY DATA FOR ISOMER SHIFT INTERPRETATION : CHEMICAL CHANGES OF

THE HIGHLY CONVERTED HIGH

MULTIPOLARITY TRANSITIONS PROBABILITIES

K. Makariùnas, E. Makariùniene, A. Dragùnas

To cite this version:

K. Makariùnas, E. Makariùniene, A. Dragùnas. COMPLEMENTARY DATA FOR ISOMER SHIFT INTERPRETATION : CHEMICAL CHANGES OF THE HIGHLY CONVERTED HIGH MULTIPO- LARITY TRANSITIONS PROBABILITIES. Journal de Physique Colloques, 1980, 41 (C1), pp.C1- 321-C1-322. �10.1051/jphyscol:19801118�. �jpa-00219600�

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JOURNAL DE PHYSIQUE Colloque C1, suppldment au no 1, Tome 41, janvier 1980, page C1-321

COMPLENENTARY DATA FOR ISOMER SHIFT INTERPRETATION : CHEMICAL CHANGES OF M E HIGHLY CONVERTED HIGH MULTI POLARITY TRANSITIONS PROBABILITIES

K . Makariiinas, E . Makariiiniene and A. Dragiinas

I n s t i t u t e of P h i s i c s , Academy of S c i e n c e s of L i t h u a n i a n SSR, 232000 V i Z n i u s , USSR.

It is well lsnomn that the same change of electron density at nucleus can be caused by different factors

-

by the change of occupation numbers of S-orbitals as well as by the screening effect connected with the change of the opposite sign of the occupation numbers of other orbitals

[l-31

.

^E.g., an increase of the occupation number ns of valence s-orbital always rai- ses electron density at nucleus, but the same increase of electron density can be resulted also by the decrease of the number n of valence p-electrons, thus the problem often arises whether a measured P

isomer shift (IS) is caused by the change ans, or by the change 4 n

p a

For simple unique interpretation of the measured IS value in terms of Ans and A

"p

additional information is necesswy

-

^the

physical quantity which would be sensitive to the sign of a n p (or ons+&

"-p

) must be measured. Some years ago Gelius [4] pain- ted out the possibility to obtain such information from the measured chemical s m s of internal electrons binding energies. In this paper we show that the answer in some cases can be obtained also measuring the sign of the chemical change a h of the probability h of the highly converted nuc- l e m electromagnetic high multipolarity transition. For this the transitions must be used for which internal conversion in p-subshells (or other subshells with high orbital quantum number) ha8 high probability.

125%e 109.27 keV Id4 transition (TlI2=

57.5 days) was used for illustration of such a possibility (for interpretation of 125~e 35e48 keV M1 transition hZ3ssbauer isomer shift). In this case internal conversion on 5s and 5p valence electrons probabilities for fully occupied valence

shell are approximately the same [5], and any decrease of the number of !&-electrons will always decrease the probability of

internal conversion on p-electrons and also the total probability of nucleax electromagnetic transition (the effect of the opposite sign, connected with the screening, is about one order of magnitude smaller). Relations among the signs of IS, ah, ans and an in this case are the following: P

Experiments were performed with 125m~e in ZnTe, CdTe and HgTe. The compounds were prepared with 125%e, which was separated from the parent isotope 125~b. The decay rates of different sources were compared by quasidifferential method similar to that described earlier in [61

.

Time dependence of the ratios of the counting rates, i.e, activities, of different samples was measured. The measurements were performed using scintillation counter of X-rays.

Geometrical conditions of measurements (fixation of the solid angle of the regi- stration system for X-rays, emerging from the source) were analogous to those used earlier in the experiments with '13sn [7].

The internal-diff erential amplitude discri- minator was used to select the pulses from the background and to controle the posi- tfon of the X-ray line in the pulse-height

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19801118

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c1-322 JOURNAL DE PHYSIQUE

spectrum. The sources were chapged every 5 minutes t o average out drifts i n e l e c t r o -

nics. The s c a l e r was governed by e l e c t r o - n i c timer with quartz s t a b i l i z a t i o n . The d a t a of the measurements were t r e a t e d with t h e a i d of computer BESN-6.

The r e s u l t s of such measurements a r e i l l u s t r a t e d i n f i g . 1, where time dependence of t h e r a t i o s R ( t ) of a c t i v i t i e s of

t h e sources ~ n ~ ~and ~~ % e~ a r e pre- ~ ~ ~ % e sented f o r two p a i r s of sources. The r e -

s u l t s p l o t t e d a r e corrected f o r t h e dead

t a b l e of r e l a t i o m among the s i g n s of IS, AA,Ans a n d n a p shows t h a t t h e increase of IS f o r HgTe as compared t o ZnTe and CdTe i s caused mainly by t h e increase of t h e occupation number n,.

BIBLIOGRAPHY

111

S.L. Ruby, Geld. Kalvius, G.B. Beard, R.E. Snyder, Phys. Rev. (1967) 239.

121 S.L. Ruby, G.K. Shenoy, Phys. Rev.

186 (1969) 326.

-

[3] J.K. Lees, P.A. Flinn, J, Chem. Phys.

g

(1968) 882,

[4] U. Gelius, Phys, S c r i p t 8

2

(1974) 133.

153 P. Rosel, H.N. F r i e s , K, Alder, H,C, P a u l i , Atomic Data and Xuclear Data Tables,

21

(1978) 91.

[6] St. G a p e a m , P. Huber, H. Leuenberger,

0,986

1

_A P. Nyikoa, Helv. Phys. Acta

42

(1970)

Time, h a l f l i v e s 45

.

Pig.1-Time dependenceof a c t i v i t i e s r a - [8] A.K, D r a g i i n a s , K . V . M a k a r i t i n a s , Fiz.

t i o s f o r two p a i r s of sources ~ n ~ ~ ~ % eTverdogo l e l a

18

(1976) 1338.

and ~ g ' ~ ~ ? I ? e .

time of t h e experimental a p p w a t u s and f o r t h e a c t i v i t y of contaminant parent 1 2 5 ~ b ( a l l corrections were determhed experi- mentally). The change ~ A o f the t r a n s i t i o n p r o b a b i l i t y

h

can be determined a f t e r the l e a s t square f i t of t h e d a t a by t h e d i r e c t l i n e R ( ~ ) s ( o ) * ( 1 - 4 A o t )

The r e s u l t s , presented i n f i g . 1, show t h a t 125%Ce i n HgTe decays a l i t t l e f a s t e r than i n ZnTe. The determined r e l a t i v e chan- ges a A /A of the M4 t r a n s i t i o n i n 1 2 5 ~ e n u c l e i p r o b a b i l i t y A a r e t h e following

( t h e weighted mean values of some experiments ) :

i n CdTe r e l a t i v e t o ZnTe

-

( 0 f l ) * l 0 - ~ , i n HgTe r e l a t i v e t o ZnTe

-

+(5*2)*10-~.

The most accurate published values of isomer s h i f t f o r TKissbauer t r a n s i t i o n i n 125Te nucleus a r e the following [8]:

f o r CdTe r e l a t i v e t o ZnTe

-

+0,06f0.06, f o r HgTe r e l a t i v e t o ZnTe

-

+0.19~0.05 ( i n mm/s).

Comparison of these data and of t h e