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Submitted on 1 Jan 1980
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SOME UNCONVENTIONAL ASPECTS OF THE NUCLEAR RESONANCE SCATTERING OF
GAMMA RAYS
J. Bara, B. Gogacz
To cite this version:
J. Bara, B. Gogacz. SOME UNCONVENTIONAL ASPECTS OF THE NUCLEAR RESONANCE SCATTERING OF GAMMA RAYS. Journal de Physique Colloques, 1980, 41 (C1), pp.C1-113-C1- 114. �10.1051/jphyscol:1980121�. �jpa-00219689�
JOURNAL DE PHYSIQUE Colloque Cl
,
supplkment au n O 1 , Tome 41, janvier 1980, page C1- 1 13SOME UNCONVENTIONAL ASPECTS OF M E NUCLEAR RESONANCE SCAllERING OF GAWW RAYS
J.J. Bara and B.F. Gogacz
Institute of Physics, JagigZZonian University, 30-059 Cracow, Reymonta 4, Poland.
A continually i n c r e a s i n g i n t e r e s t i n t h e nuclear resonance s c a t t e r i n g of gamma r a y s has been l a t e l y observed. I n this paper we r e p o r t on some unconven~ional as- p e c t s of this process concerned with t h e comparison of ~ U s s b a u e r s c a t t e r i n g and ab- s o r p t i o n e p e c t r a and with t h e a n a l y s i s of t h e Rayleigh and Compton contributions t o a s c a t t e r i n g line.
It 5 s worthwhile t o compare t h e magni- tudes of t h e dLUssbauer e f f e c t , t h e l i n e widths and t h e l i n e q u a l i t y parameters
where No, and Noff a r e the counts on- and off-resonance, respectively. *he f i r s t Zeeman l i n e s of t h e m e t a l l i c i r o n f o i l s of various thicknesses, resonant abundances p and hypothetical e l e c t r o n i c absorption c o e f f i c i e n t s p were numerically analysed.
I n eome c a s e s /Fig. l/ t h e s c a t t e r i n g method predominates t h e transmission one
ae f a r a s t h e l i n e q u a l i t y parameters (QA< QS ) and l i n e widths (
rs <
fA) a r e con- cerned. 'the magnitude of t h e MUssbauer e f f e c t of each of t h e analysed samples i s l a r g e r i n a s c a t t e r i n g than i n a trane- mission geometry.THICKNESS IN ern
Big. 1.1-Ratios of absorption QA and scat- t e r i n g QS Line q u a l i t y parameters a s fun*
t i o n s of sample thickness. & o r samples t h i c k e r than those marked by arrows t h e s c a t t e r i n g l i n e s a r e narrower than a b s o r p t i o n ones.
Conventionally t h e s c a t t e r i n g l i n e i s associated with an i n c r e a s e i n an inten- s i t y of s c a t t e r e d gamma r a y s a t t h e reson- ance energy of t h e s c a t t e r e r . However, i n eome c a s e s t h e i n t e n s i t y of s c a t t e r e d gamma r a y s can reach i t s minimum value a t t h e resonance energy. Such an unusual shape f o r a s c a t t e d n g l i n e i s expected f o r samples with small values of c r o e s s e c t i o n f o r photoeffect a s compared t o those f o r Rayleigh rind Compton s c a t t e r i n g 0 and i e due t o t h e e l e c t r o n conversion pr*
cess. A Idssbauer l i n e can be transformed from i t s t y p i c a l s c a t t e r i n g shape t o t h e
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980121
c1-114 JOURNAL DE PHYSIQUE
absorption shape by varying sample thick- The quadrupole doublets measured i n ness, e l e c t r o n i c and nuclear resonance ab- s c a t t e r i n g geometries f o r a
4x4~4
cm sorption coefficients. Line inversion i n berglium cube with some i r o n impurities s c a t t e r i n g can occur i f a small amount a r e shown i n Fig. 3*of i r o n i s embeded i n a matrix which i s composed o f ' l i g h t elements with Z values up t o 6.
Fhe i n t e g r a l eq. 24 of ref. [ 1 1 was used t o numerically c a l c u l a t e t h e shape of a s c a t t e r i n g line. Hypothetical berylium and carbon s c a t t e r e r a with i r o n i m p u r i t i e s up t o 1 at. $5 were coneidered.
For simplicity i t was aseumed t h a t t h e s c a t t e r e r s poeaees s i n g l e BbBssbauer l i n e s a t room temperature. I n o r d e r t o observe l i n e inversion f o r t h e hypothetical be-
rylium and carbon s c a t t e r e r e t h e i r o n con- c e n t r a t i o n should not exceed 0.5 at. % and 0.8 at. SY;, .respectively. These values a r e s l i g h t l y dependent on t h e 5 7 ~ e abundance and a r e limited by t h e values of t h e pho- toabsorption c o e f f i c i e n t s which strongly increase with t h e increase i n i r o n concen- tration.
Fig. 2.-Scattering l i n e s of d i f f e r e n t shapes and t h e i r Compton C, Rayleigh R and nuclear resonance N contributione.
The l i n e s shown i n Big. 2 were calculated
I , ,
-U - w -0s 0 01 40 U -U -U) -a, 0 0s (0 U V E L O C I T Y Lmmlsecl
Fig. 3.-Quadrupole doublets measured i n s c a t t e r i n g geometries.
The s c a t t e r e d 14.4 keV ganmia rays and t h e 6.47 keV conversion X-rays were detected simultanously i n t h e same geometrg by t h e same counter. The conversion X-ray quad- rupole doublets /A1 and B1/ have a t y p i c a l s c a t t e r i n g shapes while t h e corresponding ones /A2 and Bg/ obtained by r e g i s t e r i n g s c a t t e r e d gamma r a d i a t i o n posiese unusual absorption shapes.
[l] BARB J. J.
,
Investigations of Double MUesbauer Resonances, I N P ReportNO IOI?/PL, 1978.
f o r 0.1 at.
