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ELECTRONIC STRUCTURE OF SULPHUR COMPOUNDS
R. Horn, D. Urch
To cite this version:
R. Horn, D. Urch. ELECTRONIC STRUCTURE OF SULPHUR COMPOUNDS. Journal de Physique
Colloques, 1987, 48 (C9), pp.C9-1009-C9-1012. �10.1051/jphyscol:19879180�. �jpa-00227296�
JOURNAL DE PHYSIQUE
Colloque
C9, suppl6ment au n012, Tome
48,decembre 1987
ELECTRONIC STRUCTURE OF SULPHUR COMPOUNDS R.
HORNand
D. URCHChemistry Department, Queen Mary College, Mile End Road.
GB-London El 4NS, Great-Britain
Ra~m_g-
L ' e x a m i n a t i o n c i e s s p e c t . r e s r a y o n s - ) : 1::: p d u s o u f r e d a n s u n e s i r i e d e s c o m p o s i s p e r m i t I ' a n a l y s e d e l e u r s s t r u c t u r e s i l e c t r o n i q u e s p a r c e q u e l a f o r m e e t 1 ' i n t e n s i t & d ' u n p i c r a y o n - X est d & t e r m i n & p a r l a c o n t r i b u t i o n d e s o r b i t a l e s s p e c i f i c s ( p o u r S K b c ' e s t S 3 p ) au:.:o r h i t a l e s m n l e o . t l a i r e s . E c r i C v e m e n t , l e s u l f a t e , l e s u l f i t e , l e t h i o u r e a , 1 e d i b e n z o f u r a n e t 1 e s c o m p o s i s d a n s 1 e s q u e l s 1 ' o x y g 8 n e d u s u l f a t e est r e m p l a c i p a r l e m e t h y l , s o n t c o n s i d & r & s . On p e u t
d i s t i n g u e r l e s c o n t r i b u t i o n s d e S 3 p a u x o r b i t a l e s u e t s, i t a b l i r q u e d a n s l a f o r m a t i o n d e s l i a i s o n s c o v a l e n t e s l e 3 p e s t p l u s e f f i c a c e q u e l e 3s et n o t e r q u e l ' i n e r g i e s d e s p i c s s a t e l l i t e s E p ' s o n t
d e t e r m i n i e s p a r l e s a t o m e s v o i s i l - 1 5 , s o i t 1 'o:cygCne s o i t l e c a r b o n e . f l h s t r a c t E x a m i n a t i o n o f t h e 1::: p X-ray e m i s s i o n s p e c t r a f r o m s u l p h c t r i n d i f f e r e n t c o m p o u n d s e n a b l e s e l e c t r o n i c s t r u c t u r e s t o b e a n a l y s e d . T h i s i s b e c a u s e t h e s h a p e a n d i n t e n s i t y o f a n X-ray p e a k is d e t e r m i n e d b y t h e c o n t r i b u t i o n s o f s p e c i f i c o r b i t a l s ( i n t h i s c a s e S 3 p ) t o t h e m o l e c u l a r o r b i t a l s . S u l p h a t e , s u l p h i t e , t h i o u r e a , d i h e n z a f u r a n a n d compocrnds i n w h i c h t h e o:.:ygens o f s u l , p h a . t e a r e r e p l a c e d b y m e t h y l , h a v e b e e n h r i e f l y i n v e s i g a t e d . I t h a s p r o v e d p o s s i b l e t o d i s t i n g u i s h S 3 p c o n t i b u t i o n s t o u a n d s b o n d s , t o e s t a b l i s h t h a t S 3 p i s m o r e e f f e c t i v e a t o-hand f o r m a t i o n t h a n S 3s a n d t o c o n c l u d e t h a t t h e e n e r g i e s o f t h e K @ ' s a t e l l i t e p e a k s a r e d e t e r m i n e d b y t h e l i g a n d atoms, e i t h e r o x y g e n o r c a r b o n .
1. Introduction
F o r l i g h t e l e m e n t s t h e d i p o l e s e l e c t i o n r u l e i s w e l l o b e y e d s o t h a t X-r-ays a r e o b s e r v e d o n l y f o r e l e c t r o n i c : t r a n s i t i o n s i n w h i c h bE = 2 1 . I + scrct? a t r a n s i t i o n o r i g i n a t e s i n t h e v a l e n c e h a n d t h e n i t c a n b e s h o w n t h a t t h e f i n e s t r u c t u r e o f t h e r e s u l t i n g X-ray p e a k r e f l e c t s m o l e c c r l a r o r b i t a l s t r u c t u r e , b o t h i n t h e e n e r g i e s o f t , h e c o m p o n e n t p e a k s a n d i n t h e i r r e l a t i v e i n t e n s i t i e s E l l . I n i s o l a t i o n o n e s p e c i f i c t y p e o f X-ray c a n t h u s b e u s e d t o p r o b e t h e b o n d i n g r o l e o f j u s t o n e or t w o p a r t i c u l a r a t o m i c o r b i t a l s . And when many X-ray s p e c t r a a r e a l i g n e d o n a common e n e r g y s c a l e , u s i n g c o r e i o n i s a t i o n e n e r i e s d e t e r m i n e d b y X-ray p h o t o e l e c t r o n s p e c t r o s c o p y ; t h e e l e c t r o n i c s t r u c t u r e o f t h e m o l e c u l e i s r e v e a l e d E23. I n t h i s n o t e t h e a p p l i c a t i o n o f t h e s e i d e a s t o s a m e c o m p o u n d s o f s u l p h u r w i l l b e d i s c u s s e d
.
2. Experimental Procedure
T h e s u 1 , p h u r # s p e c t r a were m e a s u r e d u s i n g a P h i l i p s P W t 4 l @
s p e c t r o m e t e r w i t h a J k W s c a n d i u m a n o d e X-ray tt-tbe. T h e X - r a y s w e r e d i S f r a c t e d w i t h a g e r m a n i u m c r y s t a l . a n d d e t e c t e d i n a g a s - f l o w p r o p o r t i o n a l c o u n t e r ( 1 pm w i n d o w ) . To i m p r o v e r e s o l u t i o n b y t h e r e d u c t i o n o f ' h o r i z o n t a l d b v e r q e n c e ' a n e x t r a c o l l i m a t o r w a s p l a c e d i n t h e X-ray p a t h C31. F o r s o f t e r X - r a y s ( e . g . S L.!z,,M) a CGR Elent-163
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19879180
C9-1010
JOURNALDE
PHYSIQUEo p e n - w i n d o w X-ray t u b e w a s u s e d ; a n d t h e g e r m a n i u m c r y s t a l w a s
r e p l a c e d b y a n o r g a n i c ester w i t h a l a r g e r 2 d s p a c i n g (OHM, 6.3Snm o r OAO 9 . 1 2 n m ) 1 4 1 .
A VG ESCA I S 1 (Mk 1 ) s p e c t r o m e t . e r w a s u s e d t o r e c o r d X-ray
p h o t o e l e c t r o n s p e c t r a . E x c i t a t i o n w a s b y m e a n s o f u n m o n a c h r o m a t i s e d &Pi K a r a d i a t i o n ; s a m p l e s w e t - e m o u n t e d e i t h e r b v b e i n g p r e s s e d i n t o g o l d c o a t e d mesh o r o n s e l l a t a p e .
F i g u r e 1. S ~ . t l p h a t e XPS s o l i d l i n e S K p d o t - d a s h l i n e S L2.=M d o t t e d l i n e 0 K a d a s h e d l i n e E n e r g y s c a l e d e t e r m i n e d b y XPS
F i g u r e 2. S ~ r l p h i t e
X PS s o l i d l i n e
S P; p d o t - d a s h 1 i n e S L2.3M d o t t e d l i n e O K a d a s h e d 1 i n e E n e r g y s c a l e d e t e r m i n e d b y XPS
3. R e s u l t s a n d D i s c u s s i o n
( a ) S a h a t e a n d S u l ~ h i t e T h e s p e c t r a shown i n F i g s . 1 a n d 2 c o n f i r m
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d a t a t h a t h a v e b e e n p r e s e n t e d b y o t h e r a u t h o t - s p r e v i o u s 1 y C 5 , 6 3 . & p a r t f r-om t h e l o w - e n e r g y s t r u c . t . c t r e i n . t h e S LZq3M s p e c t r u m f r o m s u l p h i t e i o n t h e b i n c f i n g e n e r g y s c a l e 1 4 - 1 8 v ) , w h i c h p r o b a b l y i n d i c a t e s s o m e s a m p l e d e c o m p o s i t i o n 161, t h e o v e r a l l p i c t u r e s a r e r e m a r k a b l y s i m i l a r .F u r t h E ; r m o r e . t h e S K a : K p i n t e n s i t y r a t i o w h i c h c a n b e u s e d t o m o n i t o r t h e r e l a t i v e p o p u l a t i o n o f 3 p e l e c t r o n s i n a s e r i e s o f c o m p o u n d s a s t h e 2 p A e l e c t r o r i c o u n t c a n b e a s s u m e d c o n s t a n t , i s almost t h e s a m e f o r b o t h a n i o n s (SOlj- 4.2%, SO:- 4 . 1 % ) . S t t h e r e f o r e f o l l o w s t h a t t h e b o n d i n g r n l e o f . S 3 p e l e c . t r o n s i n s u l p h a t e ( 2 t = ) a n d i n s c r l p h i t e ( 4 a r + 2e) mcrst b e v e r y s i m i l a r . A l s o t h e r e is n o i n d i c a t i o n o f m o l e c u l a r o r b i t a l s w i t h b o t h 3s a n d 3 p c h a r a c t e r e x c e p t a t 3 . 8 e v ( b u t h e r e t h e 3 p c o n t r i b u t i o n , a l t h o t - c g h g i v i n g a s i g n i f i c a n t p e a k i n t h e K p s p e c t r c r m , is r e l a t i v e l y s m a l l ) . T h u s i t may b e c o n c l u d e d t h a t t h e r e i s n o s p e c t r o s c o p i c e v i d e n c e t o s u p p o r t t h e i d e a o f ' l o n e - p a i r ' i n s u l p h i t e o f m i x e d 3s a n d 3 p
c h a r a c t e r . T h e r o l e o f t h e 3s o r b i t a l s i n b o t h s u l p h a t e a n d s u l p h i t e i s s e e n t o b e r e m a r k a b l y s i m i l a r , o n l y w e a k l y b o n d i n g , w h i c h is c o n f i r m e d b y t h e v e r y s m a l l . a m o u n t o f O 2p c h a r a c t e r a t 12-14 e V . T h e h i g h - e n e r g y p e a k i n S K p (3.8 eV) i s t h u s d u e t o s m a l l a m o u n t o f 3p c h a r a c t e r i n
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4. Conclusions
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