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HAL Id: jpa-00227238

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Submitted on 1 Jan 1987

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CHLORINE 1s-13p-1 → 3p-2 X-RAY EMISSION : DEPENDENCE ON CHEMICAL ENVIRONMENT

A. Laakkonen, J. Utriainen

To cite this version:

A. Laakkonen, J. Utriainen. CHLORINE 1s-13p-1 → 3p-2 X-RAY EMISSION : DEPENDENCE ON CHEMICAL ENVIRONMENT. Journal de Physique Colloques, 1987, 48 (C9), pp.C9-749-C9-751.

�10.1051/jphyscol:19879129�. �jpa-00227238�

JOURNAL DE PHYSIQUE

Colloque C9, supplement au n012, Tome 48, decembre 1987

CHLORINE ls-'3p-' -P 3p-2 X-RAY EMISSION : DEPENDENCE ON CHEMICAL ENVIRONMENT

A. LAAKKONEN and J. UTRIAINEN*

T a m p e r e U n i v e r s i t y of T e c h n o l o g y , SF-33101 T a m p e r e , Finland

* ~ e l s i n k i U n i v e r s i t y of T e c h n o l o g y , S F - 0 2 1 5 0 E s p o o , Finland

High r e s o l u t i o n c h l o r i n e Kg x-ray s p e c t r a have been o b t a i n e d from a numbyr

of

i o n i c i n s l a t o r s . I t h a s been found t h a t t h e s a t e l l i t e t r a n s i t i o n s between I s 3p and 3p-y doubly i o n i z e d s t a t e s a r e e x t r e m e l y s e n s i t i v e t o t h e bonding. The c o r r e l a t i o n between t h e r e l a t i v e Kg s a t e l l i t e i n t e n s i t y and t h e K(J1 w i d t h i n r o c k s a l t - t y p e c r y s t a l s i s s i m i l a r t o f h e t r e n d s found i n t h e oxygen s p 6 c t r a .

Previous measurements1 i n d i c a t e t h a t t h e c h l o r i n e K B x-ray e m i s s i o n i n a l k a l i c h l o r - i d e s and i n a l k a l i n e - e a r t h c h l o r i d e s i n v o l v e s t r a n s i t i o n s between m u l t i p l y i o n i z e d s t a t e s which a r e e x t r e m e l y s e n s i t i v e t o t h e bonding. However, t h e photographic r e - c o r d i n g t e c h n i q u e p r e v e n t s a d e t a i l e d a n a l y s i s o f t h e i n t e n s i t y d i s t r i b u t i o n s .

Our c h l o r i n e Kg e m i s s i o n s p e c t r a were o b t a i n e d u s i n g a two c r y s t a l s p e c t r o m e t e r de- s c r i b e d by Suoninen and P e s s a 2

.

The s p e c t r a were e x c i t e d by t h e r a d i a t i o n from a chromium anode x-ray t u b e o p e r a t i n g a t 40 kV and 34 mA. The d e t e c t o r was a flow p r o p o r t i o n a l c o u n t e r w i t h a polypropylene window and w i t h a 90 % argon

-

10 % meth- ane m i x t u r e a t normal p r e s s u r e . We used S i 0 2 c r y s t a l s (2d = 8.49 8 ) and t h e w i d t h o f t h e ( 1 , - 1 ) curve was 0.24 eV. The s p e c t r o m e t e r was c a l i b r a t e d u s i n g t h e Pd La

1 l i n e . A l l samples were i n t h e form o f a n anhydrous powder o b t a i n e d by baking ma- t e r i a l s o f a commercial r e a g e n t g r a d e i n a vacuum. During t h e measurements t h e spec- t r o m e t e r was k e p t i n a vacuum chamber evacuated t o 1 Pa. The f o l l o w i n g c h l o r i d e samples were s t u d i e d : LiC1, NaC1, K C 1 , CsC1, MgC12, CaC12, SrC12, and BaC12. F i g u r e s 1 and 2 show t h e observed s p e c t r a .

The f e a t u r e l a b e l l e d KBx i s a t t r i b u t a b l e t o t r a n s i t i o n s between l d 1 3 p - I and 3p-2 doubly i o n i z e d s t a t e s . The I s-I 3s-I + 3s-I 3p-1 t r a n s i t i o n s a r e weak i n comparison w i t h t h e I s-I 3p-I + 3p-2 t r a n s i t i o n s 3 , and can t h u s be n e g l e c t e d . According t o t h e s h a k e model3 t h e t o t a l r e l a t i v e s a t e l l i t e i n t e n s i t y i s 39.7 % i n t h e f r e e c h l o r i n e i o n . I n t h e c a s e o f KC1 t h e observed r e l a t i v e i n t e n s i t y i s 31 ? 3 % and i t decreas- e s as one g o e s t o more c o v a l e n t r o c k s a l t - t y p e c r y s t a l s . The weakening of t h e KBx

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19879129

JOURNAL DE PHYSIQUE

F i g . 1 C h l o r i n e K p e m i s s i o n s p e c t r a o f a l k a l i c h l o r - i d e s . The e n e r g i e s 3re g i v e n r e l a t i v e t o t3e maximum o f t h e main peak K

.

T h e r e is 3 - p o i n t s m k ? h i n g i n e a c h p o i n t .

ENERGY DIFFERENCE l E V l

- 1 0 0 l o 20 30

EHERCl DIFFERENCE IEVI

-10 0 10 20 30

i 100 200 300 I00

STEP NUMBER

ENERCI DlFFERENCE I E Y I

-I0 0 10 2 0 30

F i g . 2 C h l o r i n e K p x - r a y emis- *. ~ 9 ~i~~~ 1 ~

s i o n s p e c t r a o f a l k a l i .

e a r t h - c h l o r i d e s . S p e c i - ;-- f i c a t i o n s a r e as i s =

"A

--

W, . .

F i g . 1 . . .

a

-. . . . .

1 ;

i jr,

Y . . J i

- L . . , . . , , # . J

ENERGY DIFFERENCE I E V I

ENERCI DIFFERENCE ( E l l - 2 0 ' -10 3 13 20 50 4 0 50

; b"

ENERCI DIFFERENCE IEY)

-

STEP NUMEER

ENERCI OlFFERENCE l E Y i -20 -13 3 13 23 3 0 63 50

1

ENERCI DIFFERENCE LEY) -20 -10 0 10 20 30 10 50

O LSTEP NUM8ER ; ?

band w i t h i n c r e a s i n g c o v a l e n c y i s a l s o o b s e r v e d i n a l k a l i n e - e a r t h c h l o r i d e s . I n t h e c a s e o f CsCl t h e KBx n e a r l y d i s a p p e a r s .

The b e h a v i o u r o f t h e

KR

s a t e l l i t e i n t e n s i t y i s similar t o t h e one found f o r oxy- 1 , 3

gen 1 s - ~ 2 ~ - ' + 2p-2 t r a n s i t i o n s i n o x i d e s e x c e p t f o r CsC1. I n t h e c a s e o f t h e o x i d e s a d i r e c t i o n - d e p e n d e n t r e l a x a t i o n model4 which c o n s i d e r s t h e i n f l u e n c e o f t h e c r y s t a l environment on t h e r e l a x a t i o n o f t h e 0'- 2p o r b i t a l s a c c o u n t s f o r t h e d i m i n u t i o n o f t h e s a t e l l i t e i n t e n s i t y w i t h i n c r e a s i n g c o v a l e n c y . T h i s model a l s o q u a l i t a t i v e l y

-1 -1

p r e d i c t s t h a t t h e d i s a p p e a r a n c e o f t h e I s V ⁺

v - ~

( V d e n o t e s v a l e n c e band) s a t e l - l i t e s t r u c t u r e i s accompanied by a change from a narrow f r e e - i o n - l i k e t o a broad b a n d - l i k e IS-' + V-I e m i s s i o n . The e s t i m a t e d f u l l w i d t h s a t h a l f maximum o f t h e va- l e n c e band i n a l k a l i c h l o r i d e s a r e l i s t e d i n t a b l e 1 . These v a l u e s were o b t a i n e d u s i n g a v a l u e o f 0.24 eV f o r t h e i n s t r u m e n t a l b r o a d e n i n g and 0.45 eV f o r t h e w i d t h of t h e i n i t i a l I s s t a t e . Comparison w i t h u l t r a v i o l e t 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

(UPS) r e s u l t s 5 shows t h a t t h e UPS w i d t h s a r e much l a r g e r b u t t h e s h a p e o f t h e Kf3 1 , 3 l i n e i s i n a c c o r d a n c e w i t h t h e UPS measurements o f t h e d e n s i t y o f s t a t e s o f t h e va- l e n c e band, m o d i f i e d by t h e wave-vector dependence o f t h e t r a n s i t i o n p r o b a b i l i t y .

T a b l e 1. F u l l w i d t h a t h a l f maximum (eV) and r e l a t i v e s a t e l l i t e i n t e n s i t y ( % )

-

T a r g e t From UPS P r e s e n t r e s u l t s R e l a t i v e s a t e l l i t e i n t e n s i t y ( % )

LiCl 3 . 4 2 . 8 c 0.1 4 + 2

NaCl 2.2 1 . 3

+

0.1 1 4 ? 5

CsCl 1 . 4 0 . 7 f 0.1 2

+

²

According t o t a b l e 1 t h e c o r r e l a t i o n between t h e r e l a t i v e KBx s a t e l l i t e i n t e n s i t y and t h e KB w i d t h i n r o c k s a l t - t y p e c r y s t a l s i s s i m i l a r t o t h e t r e n d s found i n t h e

1 , 3

oxygen s p e c t r a . However, s i n c e t h e r e are p r a c t i c a l l y no s a t e l l i t e s i n CsCl i n s p i t e o f i t s v e r y narrow KR l i n e t h i s i s n o t merely a r e l a x a t i o n e f f e c t , p r e d i c t e d by

173

t h e d i r e c t i o n - d e p e n d e n t r e l a x a t i o n model.

1 . C. S u g i u r a , Phys. Rev. B

2,

2679 ( 1 9 7 4 ) :

2. M. P e s s a and E. Suoninen, Phys. S c r i p t a

1,

8 9 ( 1 9 7 3 ) . 3 . T. Aberg, Phys. Rev.

156,

35 ( 1 9 6 7 ) .

4. J . V a l j a k k a , J. U t r i a i n e n , T. Aberg, and J. T u l k k i , Phys. Rev. B - 32, 6892 ( 1 9 8 5 ) . 5. R.T. P o o l e , J . G . J e n k i n , J . Liesegang, and R.C.G. Leckey, Phys. Rev. B

11,

5179

( 1 9 7 5 ) .