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Submitted on 1 Jan 1987
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EXTENDED X-RAY BREMSSTRAHLUNG ISOCHROMAT FINE STRUCTURE
E. Sobczak, J. Auleytner
To cite this version:
E. Sobczak, J. Auleytner. EXTENDED X-RAY BREMSSTRAHLUNG ISOCHROMAT FINE STRUCTURE. Journal de Physique Colloques, 1987, 48 (C9), pp.C9-1121-C9-1124.
�10.1051/jphyscol:19879204�. �jpa-00227323�
JOURNAL DE PHYSIQUE
Colloque C9, supplement au n012, Tome 48, dbcembre 1987
EXTENDED X-RAY BREMSSTRAHLUNG ISOCHROMAT FINE STRUCTURE
E. SOBCZAK and J. AULEYTNER
Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, PL-02 668 Warsaw, Poland
The extended x - r a y b r e m s s t r a h l ung i sochromat f i n e s t r u c t u r e (EXB 1 FS) has been measured f o r Pd, Ag, N i and Cu m e t a l s a t t h e p h o t o n e n e r g y o f 5415 eV. The r a d i a l d i s t r i b u t i o n f u n c t i o n s have been o b t a i n e d b y u s i n g t h e F o u r i e r t r a n s f o r m o f EXBIFS1s.
Extended x - r a y b r e m s s t r a h l u n g i sochromat f i n e s t r u c t u r e (EXB I FS) was r e p o r t e d f o r Ge a t t h e photon e n e r g y o f 5415 eV b y Sobczak e t a l . ( I ) and f o r Cu a t 1487 eV by S p e i e r e t a l . ( 2 , 3 ) . I t was d i s c o v e r e d , t h a t t h e EXBlFS o f Ge and Cu were s i m i l a r t o t h e Ge-K and Cu-K a b s o r p t i o n s p e c t r a i n t h e extended e n e r g y range (EXAFS)
.
The x - r a y b r e m s s t r a h l u n g e l e c t r o n t r a n s i t i o n s a r e p o s s i b l e f o r f i n a l e l e c t r o n s t a t e s o f a l l symmetry t y p e s , however t h e p r o b a b i l i t y o f e l e c t r o n t r a n s i t i o n s t o s and p f i n a l s t a t e s seems t o p r e d o m i n a t e o v e r t r a n s i t i o n s t o s t a t e s o f o t h e r symmetries.I n t h i s work we p r e s e n t new EXBlFS measurements a t t h e p h o t o n e n e r g y o f 5415 eV f o r Pd, Ag, N i and Cu m e t a l s p e r f o r m e d up t o a b o u t 200 eV above t h e Fermi l e v e l ( F i g . 1 ) . Owing t h e new x - r a y monochromator made o f t h e S i (220) b e n t c r y s t a l and t h e w e l l s t a b i l i z e d h i g h v o l t a g e suppl-y t h e t o t a l e x p e r i m e n t a l r e s o l u t i o n i n c l u d i n g
l i f e t i m e e f f e c t s o f t h e i n i t i a l e l e c t r o n s t a t e s i s a b o u t 1.8 eV and e.g. t h e broade- n i n g o f t h e Pd i s o c h r o m a t i s much s m a l l e r ( ~ i g . 2 ) t h a n t h e Pd-LI a b s o r p t i o n edge r e p o r t e d by D a v o l i e t a l . ( 4 ) because o f t h e n a t u r a l w i d t h o f t h e Pd-LI c o r e h o l e e q u a l t o 6 eV ( R e f . 5 ) .
A smooth a r b i t r a r y c u r v e d i s p l a y i n g t h e b a s a l shape o f each i s o c h r o m a t was found by computer f i t t i n g method and s u b s t r a c t e d f r o m each i s o c h r o m a t . The r e s u l t e d i n t e n s i t y o s c i l l a t i o n s as f u n c t i o n o f energy a r e shown i n F i g . 3 . They a r e s i m i l a r t o EXAFS's a t t h e K - a b s o r p t i o n edge f o r t h e s e m e t a l s . We have o b t a i n e d , t h a t t h e EXBlFS f r o m Pd i s s t r i k i n g l y s i m i l a r t o t h e p - t y p e p a r t i a l d e n s i t y o f e l e c t r o n s t a t e s i n Pd ( F i g . 4 ) .
A f t e r t r a n s f o r m a t i o n o f t h e EXBlFS c u r v e s f r o m t h e e n e r g y space t o t h e wave number space we have c a l c u l a t e d t h e m a g n i t u d e o f t h e F o u r i e r t r a n s f o r m o f EXBIFS1s f o r t h e i n v e s t i g a t e d m e t a l s ( F i g . 5 ) . The p o s i t i o n s o f t h e main peak o f t h e r a d i a l d i s t r i b u t i o n f u n c t i o n s i n F i g . 5, a f t e r c o r r e c t i o n s f o r t h e phase s h i f t , a g r e e w e l l w i t h n e a r e s t - n e i g h b o u r s d i s t a n c e s d i n N i , Cu, Pd and Ag m e t a l s . The b r o a d e n i n g o f o t h e r peaks i s caused by t h e h i g h t e m p e r a t u r e o f samples ( a b o u t 1100 K) d u r i n g mea- surements and b y t h e r e l a t i v e l y n a r r o w e n e r g y ranpe o f t h e measured EXBITS'S.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19879204
JOURNAL
DE
PHYSIQUEFIG. 1 . The x - r a y b r e m s s t r a h l u n g isochromats o f Pd, Ag, N i and Cu a t t h e photon energy o f 5415 eV ( p o i n t s ) and a r b i t r a r y smooth c u r v e s d i s p l a y i n g t h e b a s a l shape o f isochrornats ( s o l i d l i n e s ) .
FIG. 2. The b r o a d e n i n g o f t h e x - r a y b r e m s s t r a h l u n g isochromat o f Pd i s s m a l l e r t h a n t h e Pd-LI near edge a b s o r p t i o n spectrum measured by D a v o l i e t a l . ( 4 ) by u s i n g s y n c h r o t r o n r a d i a t i o n .
0 z
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Pd 1, XANESr l
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FIG. 3 . I n t e n s i t y o s c i 1 l a t i o n s o f x - r a y b r e r n s s t r a h l u n g i s o c h r o m a t s (EXBIFS) o f Pd, Ag, N i and Cu m e t a l s as f u n c t i o n o f energy.
FIG. 4. Comparison o f t h e EXBIFS o f Pd w i t h t h e t h e o r e t i c a l d e n s i t y o f e l e c t r o n p - t y p e s t a t e s i n Pd c a l c u l a t e d by M i i l l e r and W i l k i n s ( 5 ) .
JOURNAL DE PHYSIQUE
FIG. 5. R a d i a l d i s t r i b u t i o n f u n c t i o n s f o r N i , Cu, Pd and Ag o b t a i n e d from EXBIFS's by u s i n g t h e F o u r i e r t r a n s f o r m .
References
1. E. Sobczak, R . Goldberg, J . PeYka and J. A u l e y t n e r , i n : I n n e r - S h e l l and X-Ray P h y s i c s o f Atoms and S o l i d s , e d i t e d by D.J. Fabian, H. K l e i n p o p p e n and L.M.
Watson, Plenum, New York, 1981, pp. 529-532.
2. W. S p e i e r , J.C. Fuggle, R. Z e l l e r and M. Campagna, i n : EXAFS and Near Edge S t r u c - t u r e I l l , e d i t e d b y K . O . Hodgson, B . Hedrnan and J.E. Penner-Hahn, S p r i n g e r , B e r l i n , 1984, pp. 496-500.
3. W . S p e i e r , T.M. Hayes, J.W. A l l e n , J.B. Boyce, J.C. F u g g l e and M. Carnpagna, Phys. Rev. L e t t .
2
(1985) 1693.4. 1 . D a v o l i , S. S t i z z a , A. B i a n c o n i , M. B e n f a t o , C . F u r l a n i and V. Sessa, S o l i d S t a t e Commun. 48 (1983) 475.
5. J.E. M i i l l e r a n r ~ . ~ . W i l k i n s , Phys. Rev. 8