A MÖSSBAUER STUDY OF NUCLEAR REACTION AFTEREFFECTS

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A MÖSSBAUER STUDY OF NUCLEAR REACTION AFTEREFFECTS

A. Zhetbaev

To cite this version:

A. Zhetbaev. A MÖSSBAUER STUDY OF NUCLEAR REACTION AFTEREFFECTS. Journal de Physique Colloques, 1980, 41 (C1), pp.C1-457-C1-458. �10.1051/jphyscol:19801179�. �jpa-00219667�

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JOURNAL DE PHYSIQUE Colloque C1, supplkment au n 1, Tome 41, janvier 1980, page C1-457

A ~@SSBAUER STUDY OF NUCLEAR REACTION AFEREFFECTS

A.K. Zhetbaev

Institute of NucZear Physics, Kazakh Academy of Sciences, Alma-Ata, USSR.

I r r a d i a t i o n with charged p a r t i c l e s and neutrons causes nuclear r e a c t i o n s , equal- l y with r a d i a t i o n damages. These reac- t i o n s often r e s u l t i n t h e formation of Mtfssbauer nuclei. The cases of excited MMssbauer n u c l e i formation a r e used f o r a long time t o i n v e s t i g a t e various pbysical processes occurring around the n u c l e i i n the course of excited s t a t e l i f e t i m e fl,$

The present paper describes some cases where a s a r e s u l t of a nuclear reaction 14 t h e sample radioactive n u c l e i a r e formed t h a t decay t o produce MMssbauer nuclei, 5 7 ~ o f o r example. Nuclear reactions make it possible t o produce impurities i n Sam- p l e s , on which t h e MMssbauer e f f e c t can be observed.

Samples containing n i c k e l , manganese, and iron were used f o r t h i s investigation.

The samples were i r r a d i a t e d with cyclotron- -accelerated CC - p a r t i c l e s and protons.

Measurements were taken using a constant accelera t i o n MMssbauer spectrometer. A pro- p o r t i o n a l counter with an argon-me thane f i l l i n g served a s a detector.

Fig.1 shows the spectra of a cementite, Fe C

,

sample i r r a d i a t e d . with oC -particles.

The spectrum (a) was obtained with the 3 sample used a s an absorber. 5 7 ~ 0 i n C r with an a c t i v i t y of about 50 l n C i served a s a source. On the background of the o r i - g i n a l cementite spectrum, l i n e s appeared t h a t corresponded t o the spectrum of me- t a l l i c iron formed through the irradiatiion of the sample. The spectrum (b) was obtained when the sample was used a s a source.The absorber was potassium femocy- anide enriched with 5 7 ~ e isot;ope .The d

-

i r r a d i a t i o n of the sample induced i n it t h e r e a c t i o n 5 6 ~ e ( ~ , p ~ ) 5 7 ~ o , through which 5 7 ~ 0 was formed. I n t h e case of pro ton-irradiation

,

5 7 ~ o was formed

through r e a c t i o n s 5 6 ~ e ( p ,

T

)Y7Co and 5 7 ~ e ( ~ , n ) 5 7 ~ o.

ehannet? num8sz

Fig.1

-

Mtlssbauer s p e c t r a of . alpha-irradiated Pe C

3

The experiment has shown t h a t a l l the three reactions cause the decomposition of cementite i n t o iron and graphite. In,-- cases when the sample i s used a s a source a pure spectrum of iron can be seen,which i n d i c a t e s t h a t , f i r s t l y , due t o the nuc- l e a r reaction t h e cementite molecule de- composes without f a i l , and, secondly, no i n t e r n a l implantation occurs i n t h e sample due t o knocked-on atom wandering. Thirdly, a l l the observed components of the spectrum have no d i s t o r t i o n s o r a d d i t i o n a l components t h a t may be a t t r i b u t e d t o radiation-induced d e f e c t s o r t o the formation of new phases.

The present experiment demonstrates new p o t e n t i a l i t i e s of t h e M8ssbauer speot- roscopy f o r the two-way studying of i r r a - d i a t e d i r o n compounds o r a l l o y s t o f i n d out new pure spectrum components r i s i n g from t h e r a d i a t i o n e f f e c t .

Fig.2 shows a spectrum of an alpha- - i r r a d i a t e d manganese oxide, MnO, sample.

Under the e f f e c t of the nuclear reaction 5 % n ( ~ ,211)~~co, the sample becomes a source of 14.4 keV Mtfssbauer r - r a y s and

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19801179

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C1-458 JOURNAL DE PHYSIQUE

can be analysed with the emission method.

Potassium ferrocyanide was used a s an absorber. I n t h e spectrum, on the background of t h e i n t e n s i v e s i n g l e l i n e corresponding t o s u b s t i t u t e d ^{5 7 ~ 0}atoms An Mn, a weak a d d i t i o n a l l i n e can be seen t h a t is about 0.50 mm/s s h i f t e d r e l a t i v e t o t h e main l i n e . To r e v e a l t h e o r i g i n of t h i s addi- t i o n a l l i n e , an a d d i t i o n a l experiment was c a r r i e d out with 57~o-isotope doping i n Mn by a thermal-diffusion method. The re- corded spectrum represented a s i n g l e l i n e .

Fig.2 -Mvssbauer s p e c t r a of

y/C

o-in-M~O samples. (a) Source t MnO 57~o-doped with thermal d i f f u s i o n ; (b) Source: alpha- i r r a d i a t e d MnO.

So, it has been proved t h a t t h e addi- t i o n a l l i n e in t h e spectrum on Fig.2 is i n d i c a t i v e of r a d i a t i o n a f t e r e f f e c t s of t h e nuclear reactions. This l i n e should apparently be a t t r i b u t e d t o i n t e r s t i t i a l atoms of ^{5 7 ~ 0}i n Mn. Due t o a l i m i t e d space around them and d i s t o r t e d surround- i n g symmetry, t h e s e atoms should be pre- s e n t in a zone of higher e l e c t r o n density and should undergo t h e e l e c t r i c f i e l d gra- d i e n t e f f e c t . The former should cause an isomer s h i f t d i f f e r i n g from t h e s h i f t i n t h e s u b s t i t u t e d atoms spectrum, and t h e l a t t e r should r e s u l t in t h e quadrupole s p l i t t i n g of t h e l i n e . Therefore, t h e spectrum i n Fig.2 should be considered a s con- s i s t i n g of a s i n g l e peak an& a doublet.

A computer a n a l y s i s of t h e spectrum gives t h e following doublet parameters:

aE=0,21 W s , ~ - 0 . 6 3 d s r e l a t i v e t o 5 7 ~ o i n Mno. From the r e l a t i o n of t h e doublet and s i n g l e peak a r e a s , a conclu-

s i o n can be made t h a t about 30% of atoms d i r e c t l y c o l l i d e d w i t h a - p a r t i c l e s popu- l a t e i n t e r s t i t i a l s

,

while the r e s t sub- s t i t u t e manganese atoms i n t h e MnO lattice.

The same method of alpha-irradiation was used t o study samples of pure nickel.

A Mussbauer l a b e l i n n i c k e l was produced mainly through t h e r e a c t i o n 6 0 ~ i ( g , d ) 5 7 ~ o . The r e a c t i o n y i e l d of t h e 5 7 ~ 0 formation fcom 6 Q ~ i is higher, though 6 0 ~ i cohtent i n the n a t u r a l N i i s o t o p i c mixture i s 26.2% while 5 8 ~ i content i s 67.8%.

The emission s p e c t r a of t h e s e samples show hyperf i n e magnetic s p l i t t i n g , t h e magnetic f i e l d a t 5 7 ~ e nucleus i n N i , Hef

f ,

being 266 m e .

Control experiments with 5 7 ~ o doping by t h e thermal-diffusion method gave t h e same r e s u l t s . Thus, t h e nuclear r e a c t i o n method of producing t h e M8ssbauer l a b e l

i n pure metals agrees i n r e s u l t s with t h e thermal-diffusion l a b e l l i n g method.

I n c a s e of chemical compounds, t h e method of producing MBssbauer impuxities through nuclear r e a c t i o n s can be used f o r studying radiation-fndnced d e f e c t s i n the compounds

.

A s it is known, manganese has no Muss- bauer isotopes, and t h e MtSssbauer e f f e c t on 61~i is d i f f i c u l t t o be observed, so i t i s of no p r a c t i c a l importance.

Alpha- and proton-irradiation of sam- p l e s containing N i and Yn makes it poss- i b l e t o c a r r y out Mvssbauer s t u d i e s of N i and Mn a l l o y s and compounds. Proton- i r r a d i a t i o n of iron-containing samples gives an opportunity t o c a r r y o u t two- -way i n v e s t i g a t i o n s with t h e aim of re- v e a l i n g nuclear r e a c t i o n a f t e r e f f e c t s .

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