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EXAFS IN DISPERSIVE MODE, A NEW TOOL FOR STUDYING IN SITU KINETICS : EXAMPLE OF ELECTROCHEMICAL INCLUSION OF COPPER
SPECIES IN AN ORGANIC CONDUCTOR
E. Dartyge, A. Fontaine, G. Tourillon, A. Jucha
To cite this version:
E. Dartyge, A. Fontaine, G. Tourillon, A. Jucha. EXAFS IN DISPERSIVE MODE, A NEW TOOL
FOR STUDYING IN SITU KINETICS : EXAMPLE OF ELECTROCHEMICAL INCLUSION OF
COPPER SPECIES IN AN ORGANIC CONDUCTOR. Journal de Physique Colloques, 1986, 47
(C8), pp.C8-607-C8-614. �10.1051/jphyscol:19868114�. �jpa-00226012�
JOURNAL DE PHYSIQUE
Colloque C8, suppl6ment au n o 12, Tome 47, dgcembre 1986
EXAFS IN DISPERSIVE MODE, A NEW TOOL FOR STUDYING IN SITU KINETICS : EXAMPLE OF ELECTROCHEMICAL INCLUSION OF COPPER SPECIES IN AN ORGANIC CONDUCTOR
E. DARTYGE, A. FONTAINE, G. TOURILLON and A. JUCHA LURE, (Laboratoire CNRS, CEA, MEN), Bdtiment 2090, F-91405 Orsay Cedex, France
R e s u m e : Les m e c a n i s m e s et l e s c i n e t i q u e s d ' i n c l u s i o n e l e c t r o c h i m i q u e d'especes c u i v r i q u e s dans l e p o l y 3methylthioph'ene ( p o l y m 8 r e o r g a n l q u e c o n d u c t e u r ) ont e t e etudies i n s i t u p a r s p e c t r o s c o p i e s ' a b s o r p t i o n x en mode d i s p e r s i f . Les m e s u r e s EXAFS, c o m p l e m e n t a i r e s des r e s u l t a t s deja obtenus p a r XANES, p e r m e t t e n t de d i s t i n g u e r t r o i s etapes d i s t i n c t e s :
- Reduction r a p i d e de cu2%n ~ u ~ % o r n ~ l e x 6 p a r 1'oxygkne du dopant u t i l i s e l o r s de l a s y n t h e s e du p o l y m e r e (S03CF3)-
- F i x a t i o n des nouveaux i o n s c u l + f o r m e s p a r l e s atomes de s o u f r e du p o l y 3meth y l t h i o p h e n e
-
C r o i s s a n c e de p l a q u e t t e s (1 11) m e t a l l i q u e s de c u i v r e A b s t r a c tThe m e c h a n i s m s and t h e k i n e t i c s f o r t h e e l e c t r o c h e m i c a l i n c l u s i o n 01 c o p p e r s p e c i e s i n s i d e p o l y 3 m e t h y l t h i o p h e n e ( a n o r g a n i c c o n d u c t i n g p o l y m e r ) h a v e b e e n s t u d i e d i n s i t u b y d i s p e r s i v e x r a y a b s o r p t i o n s p e c t r o s c o p y .
The
EXAFS r e s u l t s compl'ement t h e t h r e e c h e m i c a l s t e p $ p r e v i o u s l y deduced f r o m XANES and t h e n a t u r e of c h e m i c a l bonds f o r m e c d u r i n g t h e i n c l u s i o n s p r o c e s s e s a r e t h e n p r e c i s e d :- a f a s t cu2'-t c u l + r e d u c t i o n w h e r e t h e CU" i o n s a r e complexed by t h e 0 atoms coming f r o m t h e dopant used d u r i n g t h e p o l y m e r s y n t h e s i s (S03CF3)-
- F i x a t i o n of t h e new s y n t h e t i z e d C U ' ~ ~ O ~ S on t h e S atoms of p o l y 3 m e t h y l t h i o p h e n e
- G r o w i n g of ( 1 1 1 ) m e t a l l i c c o p p e r p l a t e l e t s .
I n t r o d u c t i o n
Organic conducting p o l y m e r s r e p r e s e n t a new c l a s s of m a t e r i a l whose c o n d u c t i v i t y c a n v a r y c o n t i n u o u s l y b e t w e e n an i n s u l a t o r - s e m i c o n d u c t i n g s t a t e t o a c o n d u c t i n g s t a t e upon doping. A m o n g a l l t h e s e compounds,
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19868114
C8-608 JOURNAL DE PHYSIQUE
p o l y t h i o p h e n e and d e r i v a t i v e s ( ' ) a p p e a r t o be t h e m o s t p r o m i s i n g , due t o t h e i r h i g h s t a b i l i t y a g a i n s t o x y g e n and m o i s t u r e b o t h i n t h e i r doped and d e d o p e d f o r m s . Thus p r a c t i c a l a p p l i c a t i o n s i n t h e f i e l d s o f o r g a n i c b a t t e r i e s , d i s p l a y d e v i c e s o r p h o t o v o l t a i c s y s t e m s h a v e b e e n t e s t e d . M o r e o v e r w e h a v e s h o w n (') t h a t s m a l l m e t a l l i c p a r t i c l e s c a n be e l e c t r o c h e m i c a l l y i n c l u d e d i n p o l y 3 m e t h y l t h i o p h e n e PMeT which l e a d s t o new i n t e r e s t i n g c a t a l y t i c p r o p e r t i e s . However t h e s e c h a r a c t e r i s t i c s depend s t r o n g l y on t h e c h e m i c a l n a t u r e and t h e sizes of t h e p a r t i c l e s .
A f i r s t s e t of XANES e x p e r i m e n t s ( 3 ) on a c a t h o d i c a l l y p o l a r i z e d PMeT f i l m i m m e r s e d i n an aqueous Cu C12 s o l u t i o n has been r e c o r d e d i n s i t u using t h e d i s p e r s i v e x - r a y a b s o r p t i o n s p e c t r o s c o p y . It has r e v e a l e d t h e existence of t h r e e c h e m i c a l r e a c t i o n s :
1) a f a s t p a r t i a l c u 2 + + c u l + t r a n s f o r m a t i o n (time c o n s t a n t = 27s) l u s t when t h e p p l a r i z a t i o n i s a p p l ~ e d . 1 1 ) ' ~ s e c o n d k i n e t ~ c i n c r e a s i n g t h e c u f content b u t w i t h a s l o w e r t i m e c o n s t a n t (-600 s). 111) The a p p a r e n c e o f m e t a l l i c c o p p e r c l u s t e r s whose s i z e i n c r e a s e s a c c o r d i n g t o t h e p o l a r i z a t i o n t i m e . These e l e c t r o c h e m i c a l p r o c e s s e s have been e a s i l y d e t e c t e d because : i) an x - r a y a b s o r p t i o n s p e c t r u m can be r e c o r d e d i n a t i m e as s h o r t as 8ms w i t h t h e d i s p e r s i v e sheme and (ii) t h e XANES f e a t u r e s o f each cu2+ c u l + and Cu" s p e c i e s a r e w e l l d e f i n e d and m o s t l y r e l a t e d t o t h e i r i o n i c c h a r g e and t h e i r c h a r a c t e r i s t i c m u l t i p l e s c a t t e r i n g o s c i l l a t i o n s . Thus t h e e v o l u t i o n of c o n c e n t r a t i o n w i t h t h e e l e c t r o c h e m i c a l t r e a t e m e n t f o r each s p e c i e s have been d e t e r m i n e d . However, s e v e r a l p a r a m e t e r s w e r e n o t p r e c i s e l y known and w e r e connected w i t h i) t h e n a t u r e of t h e i n t e r a c t i o n s between t h e dopant and t h e p o l y m e r , i i ) t h e l o c a l e n v i r o n m e n t of t h e t h r e e c o p p e r species and i i i ) t h e s i t e s o f c o m p l e x a t i o n f o r CU" and Cu0.
We r e p o r t i n t h i s w o r k an i n s i t u d i s p e r s i v e EXAFS s t u d y p e r f o r m e d i n t h e s a m e c o n d i t i o n s t h a t t h e p r e v i o u s XANES i n v e s t i g a t i o n s w h e n PMeT i s c a t h o d i c a l l y p o l a r i z e d i n a Cu C12 aqueous s o l u t i o n . The data unambiguously show t h a t
i ) t h e f i r s t s y n t h e t i z e d CU" i o n s a r e c o m p l e x e d b y t h e oxygen coming f r o m t h e S04CF3- dopant
i i ) t h e s e c o n d c h e m i c a l s t e p c o r r e s p o n d s t o t h e f i x a t i o n of t h e ~ u ' + i o n s on t h e s u l f u r atoms of PMeT and
i i i ) t h e f i r s t m e t a l l i c c o p p e r c l u s t e r s g r o w w i t h a (1 1 1 ) p l a t e l e t l i k e s t r u c t u r e .
I 1 S a m ~ l e p r e ~ a r a t i o n and e x ~ e r i m e n t
PMeT i s e l e c t r o c h e m i c a l l y g r a f t e d on a Pt w i r e i n CH3CN-5 10-'M N ( B u ) ~ S.03CF3 - 5 10-'M 3 m e t h y l t h i o p h e n e e l e c t r o l y t i c medium. The P t e l e c t r o d e i s a n o d i c a l l y p o l a r i z e d a t 1.35 V/SCE ( s a t u r e d c a l o m e l e l e c t r o d e ) t o obtain t h e d o p e d c o n d u c t i n g p o l y m e r w h e r e t h e o x i d i z e d p o l y m e r i c c h a i n s a r e a s s o c i a t e d w i t h t h e S03CF3- i o n s ; i n t h e s e conditions, t h e doping l e v e l of
PMeT l i e s i n t h e r a n g e 25-301. T h i s m o d i f i e d e l e c t r o d e i s r i n c e d , d r i e d a n d p u t i n a 3 m m t h i c k e l e c t r o c h e m i c a l c e l l c o m p o s e d o f a t e f l o n r i n g c o v e r e d b y t w o k a p t o n w i n d o w s . A c o p p e r c h l o r i d e s o l u t i o n (H20-50 mM Cu C12, PH=6) i s t h e n p o u r e d i n t o t h e c e l l . A t w o e l e c t r o d e s c o n f i g u r a t i o n i s u s e d t o p e r f o r m t h e c o p p e r i n c l u s i o n s : t h e g r a f t e d e l e c t r o d e a n d a Pt w i r e .
The f o c u s s e d x - r a y b e a m i s a d j u s t e d t o p a s s t h r o u g h t h e p o l y m e r c l o s e t o t h e Pt w i r e . S i n c e t h e s a m p l e a t t e n u a t e s t h e x - r a y b e a m b y a f a c t o r o f a b o u t 80, 3 4 0 m s w e r e c h o s e n t o c o m p l e t e a s l n g l e s p e c t r u m w i t h a b o u t
l o 8
p h o t o n s
.
I n f a c t , e a c h s p e c t r u m i s t h e a d d i t i o n o f 8 c o n s e c u t i v e a c c u m u l a t i o n s a n d t h e a c q u i s i t i o n w a s r e p e a t e d each 3 . 8 s .C o m p a r i n g t h e j u m p o f t h e a b s o r p t i o n e d g e o f t h e 3 m m t h i c k c e l l f i l l e d w i t h t h e Cu C12 a q u e o u s s o l u t i o n w i t h a n d w i t h o u t t h e p o l y m e r , w e k n o w t h a t a t m o s t 6 4 % o f t h e i n v e s t i g a t e d v o l u m i s f i l l e d w i t h t h e s o l u t i o n , w h i l e t h e p o l y m e r e f i b e r s t a k e t h e r e m a i n i n y 3 6 % o f t h e v o l u m e .
The EXAFS s p e c t r a ? a v e b e e n r e c o r d e d u s i n g t h e d i s p e r s i v e EXAFS l i n e a t DCI. T h e s e e x p e r i m e n t s h a v e b e e n d o n { u s i n g a t r i a n g u l a r s h a p e d Si (1 11) c r y s t a l b e n t i n o r d e r t o & a r y c o n t i n u o i ~ s l y t h e g l a n c i n g a n g l e of t h e i n c i d e n t x r a g s . A c c o r d i n g t o t h e " c u r v a t u r e a n d t h e a v e r a g e B r a g g a n g l e r e l a t e d t o t h e e n e r g y o f t h e e d g e o f i n t e r e s t t h e 2 3 c m l o n g c r y s t a l c a n r e f l e c t a b a n d w i d t h l a r g e e n o u g h t o c o l l e c t a f u l l EXAFS s p e c t r u m . A t t h e c o p p e r K-edge a 8 0 0 eV-wide b a n d p a s s i s a c h i e v e d w h e n t h e b e n d i n g r a d i u s i s a b o u t 7 m e t e r s . T h e s e l e c t e d b e a m c o n v e r g e s a n d f o r m s a 800 p - w i d e f o c a l s p o t ( 5 ) . T h e e l e c t r o c h e m i c a l c e l l i s i n s e r t e d a t t h i s f o c u s p o i n t . T h e t r a n s m i t t e d b e a m i s d e t e c t e d b y a - p h o t o d i o d e a r r a y m a d e o f 1024 s e n s i n g e l e m e n t s 2 5 ~ - w i d e e a c h w h i c h i s c a p a b l e o f m e a s u r i n g t h e h i g h X - r a y f l u x s u p p l i e d b y t h e s y n c h r o t r o n r a d i a t i o n s o u r c e ( 1 0 ' ~ - 1 0 ~ c p s a f t e r t h e c r y s t a l ) . T h e e n e r g y r e s o l u t i o n o f t h i s d e t e c t o r i s d e t e r m i n e d b y t h e s i z e s o f t h e p i x e l a n d f o c a l s p o t a n d t h e d i s t a n c e b e t w e e n them, a n d i s c o m p u t e d t o b e 2 . 5 eV f o r t h e Si(1 11) ( F i g . 1). T h e r e i s s u f f i c i e n t f a s t m e m o r y s o t h a t w e a r e a b l e t o c o l l e c t 6 0 s p e c t r a o f 1024 d a t a o f 1 6 b i t - l o n g w o r d s a t a t i m e . I n a d d i t i o n , a LOG-ROM t a b l e a l l o w s r a p i d c o m p u t a t i o n a n d d i s p l a y o f t h e 6 0 a b s o r p t i o n s p e c t r a .
R e s u l t s a n d d i s c u s s i o n XANES
T h e evolution o f t h e XANES f e a t u r e s w i t h t h e p o l a r i z a t i o n t i m e r e p r o d u c e d e x a c t l y t h o s e a l r e a d y o b t a i n e d d u r i n g t h e f i r s t s e t o f e x p e r i m e n t s . The t h r e e m o s t c h a r a c t e r i s t i c s s p e c t r a a r e d i s p l a y e d i n F i g . 1 . T h e c u 2 + s p e c t r u m i s s h i f t e d b y 8 . 5 eV f r o m t h e Cu" e d g e a n d s h o w s a n i m p o r t a n t w h i t e l i n e d u e t o t h e o c t a e d r a l s y m m e t r y o f t h e s i x w a t e r m o l e c u l e s w h i c h c o m p l e x t h e c u 2 + i o n . T h e C U ~ + - O b o n d l e n g t h i s t h e r e g u l a r o n e 1 . 9 5 A " . D u r i n g t h e e l e c t r o c h e m i c a l t r e a t m e n t , a b u m p a p p e a r s o n t h e l o w e n e r g y s i d e w i t h a d e c r e a s e o f t h e w h i t e l i n e i n t e n s i t y r e l e v a n t t o t h e f o r m a t i o n o f c u l f i o n s . F o r l o n g e r p o l a r i z a t i o n t i m e , m e t a l l i c Cu
p a r t i c l e s a r e s y n t h e t i z e d , c h a r a c t e r i z e d b y t h e t y p i c a l o s c i l l a t i o n s c l o s e t o t h e edge.
C8-6 10 JOURNAL DE PHYSIQUE
EXAFS
A s e l e c t e d s e t of t h e k 3 - w e i g h t e d F o u r i e r t r a n s f o r m s u s i n g a 350eV-wide window a r e shown i n Fig.2
.
One c a n o b s e r v e as a f i r s t e v o l u t i o n (2a-12b) a s h i f t of t h e p r i n c i p a l peak t o w a r d s t h e s h o r t distances, as w e l l as a b r o a d e n i n g (At=160s). A f t e r 168s t h i s peak i s s p l i t t e d i n t o t w o components (2c) w h o s e i n t e n s i t y r a t i o i n v e r t s w i t h t h e p o l a r i z a t i o n t i m e . The f a s t e v o l u t i o n o f t h e s y s t e m i s i l l u s t r a t e d i n F i g . 3 w h i c h c o r r e s p o n d s t o t w o c o n s e c u t i v e s p e c t r a s e p a r a t e d b y o n l y 8 s e c . I f t h e e l e c t r o c h e m i c a l t r e a t m e n t i s p e r s u e d , a s h o u l d e r a p p e a r s a t l o n g d i s t a n c e on t h e m a i n peak which becomes m o r e and m o r e p r o n o u n c e d . A f t e r 280 sec, a unique peak i s o b s e r v e d which s h i f t s c o n t i n u o u s l y t o w a r d s l o n g e r d i s t a n c e s .A t t h i s stage, t h e i n t e n s i t y of t h e FT peak i n c r e a s e s , i n d i c a t i n g t h a t t h e a t o m s o f t h e f i r s t s h e l l h a v e e i t h e r a l o n g e r b a c k s c a t t e r i n g amplitude, o r t h a t t h e i r n u m b e r i n c r e a s e s . A t t h e end of t h e p r o c e s s , t h e c h a r a c t e r i s t i c FT of m e t a l l i c c o p p e r i s obtained (2c), w i t h i n a d d i t i o n a r e m a i n i n g l i t t l e peak at s h o r t d i s t a n c e s . Fig. 4 a b c d shows t h e f i l t e r e d b a c k t r a n s f o r m e d s p e c t r a of t h e f i r s t s h e l l . T h e s e c u r v e s a r e c h a r a c t e r i z e d by a continuous d e c r e a s e of t h e a m p l i t u d e of t h e o s c i l l a t i o n s w i t h t h e a p p e a r a n c e of a beat node at a b o u t 2 5 0 eV ( f i g . 4 ~ ) d i r e c t l y r e l a t e d t o t h e s p l i t t i n g of t h e F o u r i e r t r a n s f o r m . This b e a t node c l e a r l y shows t h a t t w o d i f f e r e n t atoms w i t h a TI d i f f e r e n c e i n t h e i r phase s h i f t s c o n t r i b u t e t o t h e EXAFS o s c i l l a t i o n s . The o n l y p o s s i b i l i t y t o e x p l a i n i t i n v o l v e s 0 and S e l e m e n t s i n t h e f i r s t c o o r d i n a t i o n s h e l l .
This hypotheses i s r e i n f o r c e d by t h e EXAFS c h a r a c t e r i s t i c s of Cu2O and Cu2S t a k e n as r e f e r e n c e s which e x h i b i t a TI d i f f e r e n c e s i n t h e i r phase s h i f t s ( f i g . 5).
Thus t h e f i r s t c h e m i c a l s t e p c o r r e s p o n d s t o t h e f o r m a t i o n of c u l + ions c o m p l e x e d b y 0 a t o m s coming f r o m t h e (S03CF3)- dopant u s e d d u r i n g t h e p o l y m e r s y n t h e s i s .
The s e c o n d s t e p i s c l e a r l y i d e n t i f i e d as t h e f i x a t i o n of new s y n t h e t i z e d
C U ' + i o n s b y t h e S a t o m of t h e p o l y m e r i t s e l f . F i n a l l y m e t a l l i c c o p p e r c l u s t e r s a r e f o r m e d . I n o r d e r t o p r e c i s e t h e amounts o f each c o p p e r species i n s i d e t h e p o l y m e r i c m a t r i x , we h a v e c a l c u l a t e d t h e o r e t i c a l F o u r i e r t r a n s f o r m s using t h e CuZO, Cu2S and Cu" a m p l i t u d e and p h a s e s h i f t v a l u e s .
S e v e r a l c o n c l u s i o n s can be pushed out :
i) t h e b r o a d e n i n g o f t h e peak o b s e r v e d a f t e r -80 sec r e s u l t s f r o m t h e p r e s e n c e o f cu2+-0, c u l + - 0 and cul+-s species, i i ) t h e s p l i t t i n g of t h e peak i s r e p r o d u c e d when o n l y cul+-0 and cul+-s a r e c o n s i d e r e d which excludes t h e p r e s e n c e of c u 2 + atoms, iii) t h e f u r t h e r e v o l u t i o n of t h e FT f o r l o n g e r p o l a r i z a t i o n t i m e a r e r e l e v a n t t o t h e f o r m a t i o n of m e t a l l i c c o p p e r c l u s t e r s i n t h e m a t r i x i v ) f i n a l l y t h e i n t e n s i t y r a t i o f o r t h e 3 t h and 4 t h s h e l l i s i n v e r t e d when c o m p a r e d t o t h e b u l k c f c m e t a l l i c c o p p e r : t h i s i m p l i e s t h a t t h e e a r l y stages of m e t a l l i c c l u s t e r i n g i n v o l v e s a (1 1 1 ) p l a t e l e t g r o w t h since
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f i g 4
t h e d i s t a n c e s i n s i d e t h e (1 11) p l a n e s a r e p r e f e r e n t i a l l y o b s e r v e d t o t h e d i s t a n c e s between p l a n e s .
However one m u s t point out t h a t t w o p r o b l e m s r e m a i n u n s o l v e d : i) t h e d i s c r e p a n c y d e t e c t e d i n t h e e v o l u t i o n s of t h e XANES and EXAFS c h a r a c t e r i s t i c s f o r t h i s e x p e r i m e n t .
ii) t h e d i f f e r e n c e i n t h e a m p l i t u d e v a l u e of t h e TF obtained t h e o r e t i c a l l y and e x p e r i m e n t a l l y which l i e s i n t h e r a n g e of 25-30%.
This l a s t p o i n t s h o u l d come f r o m t h e c h e m i c a l n a t u r e of t h e compounds t a k e n as r e f e r e n c e s . I t ' s obvious t h a t t h e d i f f e r e n t c o p p e r environment i n c l u d e d i n t h e p o l y m e r may be d i f f e r e n t of t h e c r y s t a l l i z e d m a t e r i a l s . The o v e r a l l n u m b e r of n e i g h b o u r s i s p r o b a b l y d i f f e r e n t i n t h e p o l y m e r f r o m i t i s i n t h e s t a n d a r t s , even i f t h e i o n i c bond l e n g t h s m u s t be kept w i t h o u t m a j o r changes. A n ab-initio f i t t i n g of t h e EXAFS data w i l l g i v e a m o r e d e f i n i t e a n s w e r p r o v i d i n g p h a s e - s h i f t s and a m p l i t u d e c a n be e x t r a c t e d f r o m s u i t e d s a m p l e s .
Conclusion
The d i s p e r s i v e x r a y a b s o r p t i o n s p e c t r o s c o p y d u r i n g t h e i n s i t u e l e c t r o c h e m i c a l c o p p e r i.nclusion p r o c e s s e s i n s i d e PMeT a l l o w e d us t o p r e c i s e a l l t h e c h e m i c a l s t e p s w h l c h l e a d t o t h e f o r m a t i o n o f m e t a l l i c c o p p e r a g g r e g a t e s :
-
a r a p i d Cu2+-+ C u l i t r a n s f o r m a t i o n w h e r e t h e Cul' i o n s a r e com.plexed by t h e oxygen atom comi-ng f r o m t h e S03CF3 dopant.- a second k i n e t i c domain w h e r e t h e new s y n t h e t i z e d CU" i o n s a r e f i x e d on t h e s u l f u r atoms of PMeT.
-
t h e f i r s t m e t a l l i c c o p p e r c l u s t e r s g r o w w i t h a (1 11) p l a t e l e t l i k e s t r u c t u r e .The d i s p e r s i v e a b s o r p t i o n s p e c t r o s c o p y i s w e l l a d a p t e d t o f o l l o w k i n e t i c s t u d i e s of chemical r e a c t i o n s and s t r u c t u r a l m o d i f i c a t i o n s . The good s i g n a l n o i s e r a t i o g i v e s t h e p o s s i b i l i t y of studying d i l u t e s y s t e m s .
F u r t h e r developments of t h e p r e s e n t s t u d y d e a l w i t h t h e i n i t i a t i o n and t h e e a r l y stages of c o p p e r c l u s t e r i n g .
Using i s o m o r p h o u s p o l y s e l e n o p h e n e p o l y m e r s and o t h e r dopants w i l l g i v e us new s y s t e m s t o check t h e ideas developped i n t h i s p a p e r .
References
1 ) G. T o u r i l l o n "Handbook on conjugated e l e c t r i c a l l y conducting p o l y m e r s "
Ed.T. Skotheim, M a r c e l Dekker 1 chap. 9 p. 294 (1986)
2 )
G. T o u r i l l o n and F. G a r n i e r J Phys. Chem.88
5281 (1984)C8-6 14 JOURNAL DE PHYSIQUE
3 ) G. T o u r i l l o n , E . Dartyge, A . Fontaine and A . Jucha Phys. Rev. L e t t . i n p r e s s
4) E . Dartyge, C. Depautex, J . M . Dubuisson, A. Fontaine, A. Jucha, P . L e b o u c h e r and G. T o u r i l l o n SRI S t a n f o r d J u l y 85, N I M
5) This i s t w i c e as m u c h as we obtained w i t h a 7 c m l o n g c r y s t a l . This a b e r r a t i o n e f f e c t s h o u l d be r e d u c e d by using an a p p r o p r i a t e shape of t h e c r y s t a l i n o r d e r t o a l l o w a bending c l o s e t o t h e i d e a l e l l i p t i c a l p r o f i l e . F i a u r e captions
- 1) E v o l u t i o n of t h e c o p p e r XANES s p e c t r a v e r s u s p o l a r i z a t i o n t i m e : a) 0 sec, b) 160 sec, c) 168 sec, d) 200 sec, e) 460 s e c .
- 2) P r i n c i p a l steps of e v o l u t i o n s of t h e k3 F o u r i e r t r a n s f o r m s v e r s u s p o l a r i z a t i o n time.Same steps as i n f i g . 1
- 3) k 3 F o u r i e r t r a n s f o r m s of t w o c o n s e c u t i v e s p e c t r a s e p a r a t e d by 8 s e c . Note t h e i n v e r s i o n of t h e i n t e n s i t y r a t i o f o r t h e t w o peaks of t h e f i r s t s h e l l .
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4) F o u r i e r b a c k t r a n s f o r m e d c o p p e r s p e c t r a . Same s t e p s as i n f i g . 2 . - 5) F o u r i e r b a c k t r a n s f o r m e d s p e c t r a of s t a n d a r d s :a) aqueous Cu C I 2 solution, b) Cu20, c) Cu2S, d) m e t a l l i c c o p p e r f o i l
