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A STUDY OF MOLECULAR EFFECTS IN BEAM-FOIL SPECTROSCOPY
B. Andresen, S. Hultberg, B. Jelenković, L. Liljeby, S. Mannervik, E. Veje
To cite this version:
B. Andresen, S. Hultberg, B. Jelenković, L. Liljeby, S. Mannervik, et al.. A STUDY OF MOLECULAR
EFFECTS IN BEAM-FOIL SPECTROSCOPY. Journal de Physique Colloques, 1979, 40 (C1), pp.C1-
352-C1-353. �10.1051/jphyscol:1979176�. �jpa-00218456�
JOURNAL DE PHYSIQUE Colloque C1, supplPment au n o 2, Tome 40, fdvrier 1979, page C1-352
A STUDY OF MOLECULAR EFFECTS I N BEAM-FOIL SPECTROSCOPY
B. I i n d r e s e n a ) , S. ~ u l t b e r g ~ )
,
B. ~ e l e n k o v i b ~ ) , L. ~ i l j e b y ~ ) , S. *annervikb) and E. vejeab' a ) ~ h y s i c s L a b o r a t o r y 11, H. C . 0 r s t e d I n s t i t u t e , U n i v e r s i t e t s p a r k e n 5, DK-2100 Copenhagen 8Denmark
b ) ~ e s e a r c h I n s t i t u t e f o r P h y s i c s , Roslagsvzgen 100, S-104 05 Stockholm 50, Sweden
R6sum6. Nous avons 6 t u d i 6 l a r a d i a t i o n o p t i q u e & i s e p a r d e s p ~ o j e $ t i l $ s m v n o a t o ~ i q u e s s u i v a n t l ' e x c i t a t i o n beam-foil d e s f a i s c e a u x d e H
,
H 2 , H3, 0 e t 0 2 .A b s t r a c t . We have i n v e s t i g a t e d t h e o p t i c a l r a d i a t i o n from t $ e mqnatvmic p $ o j e c t i ) e s f o l l o w i n g beam-foil e x c i t a t i o n u s i n g beams of H
,
H z , H3, 0 and 0 2 .We have i n v e s t i g a t e d t h e o p t i c a l r a d i a t i o n from t h e monatomic p r o j e c t i l e s f o l l o w i n g beam-foil e x c i t a t i o n u s i n g beams
+ + + +
o f H+, H 2 , H 3 , 0 and 02. When beams of monatomic s p e c i e s a r e u s e d , t h e r e i s
e s s e n t i a l l y z e r o p r o b a b i l i t y f o r h a v i n g two p r o j e c t i l e s i n t h e f o i l a t t h e same time, whereas a t l e a s t two p r o j e c t i l e n u c l e i a r e c l o s e t o g e t h e r f o r i n c i d e n t m o l e c u l a r p a r t i c l e s . Thus, i n f o r m a t i o n a b o u t t h e i n t e r a c t i o n between a t o m i c p a r t i c l e s and s o l i d s may be o b t a i n e d by comparing t h e outcome u s i n g d i f f e r e n t beams o f t h e same element.
The a c c e l e r a t e d a t o m i c and m o l e c a l a r i o n s were s e n t t h r o u g h c a r b o n
f o i l s o f t h i c k n e s s 1 2 ~ g / c m 2
,
t h e o p t i c a l r a d i a t i o n d e t e c t e d p e r p e n d i c u l a r t o t h e beam d i r e c t i o n , and t h e p r o j e c t i l e s were f i n a l l y e n e r g y a n a l y z e d i n a n e l e c t r o s t a t i c a n a l y z e r 111. The a c c e l e r a t o r h i g h t e n s i o n was a d j u s t e d s o t h a t t h e p r o j e c t i l e s had t h e same e n e r g y a f t e r t h e f o i l . I n t h e measurements w i t h d i f f e r e n t hydrogen beams,t h e e x i t p r o t o n e n e r g y was 100 keV, and t h e measurements w i t h oxygen were c a r r i e d o u t a t e x i t e n e r g i e s of 100 keV and 155 keV.
The beam c u r r e n t was measured w i t h no f o i l i n t h e beam p a t h , and t h e photon y i e l d s were i n a l l c a s e s r e f e r r e d t o t h e same f l u x o f incoming p r o j e c t i l e n u c l e i ( i . e .
c o u n t s two, e t c . 1.
H : The hydrogen r e s u l t s a r e shown i n
PRINCIPAL OUANlUM NUMBER, n
F i g . 1
-
R e l a t i v e p o p u l a t i o n s o f n s+
nd l e v e l s i n hydrogen a s f u n c t i o n s o f t h e p r i n c i p a l quantum number n , u s i n g . v a r i o u s m o l e c u l a r incoming beams.t h e f i g u r e t o g e t h e r w i t h some d a t a
o b t a i n e d a t 25 keV p e r p r o t o n i n Copenhagen.
We s e e f o r a l l l e v e l s o b s e r v e d a n i n c r e a s e i n t h e i n t e n s i t y o f e l e c t r o n i c t r a n s i t i o n s o f a p p r o x i m a t e l y 25% when g o i n g from a p r o t o n beam t o a n H2
+
beam and a f u r t h e r i n c r e a s e o f a p p r o x i m a t e l y 25% when H3+
i sArticle published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979176
a c c e l e r a t e d . T h i s e f f e c t i s i n d e p e n d e n t o f t h e l e v e l of e x c i t a t i o n and t h u s a c t u a l l y a s t a t e m e n t a b o u t t h e c h a r g e s t a t e o f t h e emergent atom, i n agreement w i t h e a r l i e r c h a r g e s t a t e d i s t r i b u t i o n measurements done w i t h H+ and H: beams 121. Very few molecu- l a r i o n s s u r v i v e p a s s a g e t h r o u g h t h e f o i l , s o e s s e n t i a l l y a l l f i n a l p a r t i c l e s a r e s i n g l e atoms r e g a r d l e s s of which beam i s used. However, t h o s e H2
+
i o n s which e n t e r t h e f o i l c o l l i n e a r l y may t r a v e l t o g e t h e r t h r o u g h t h e f o i l i n s u c h a way t h a t t h e second p r o t o n i s c a r r i e d a l o n g i n t h e n e g a t i v e wake p o t e n t i a l o f t h e f i r s tp r o t o n [31 a t a d i s t a n c e of a few angstroms.
Behind t h e f o i l t h e H2
++
system w i l l s u f f e r a Coulomb e x p l o s i o n s o t h a t o n l y s i n g l e atoms a r e d e t e c t e d , b u t t h e d o u b l e c h a r g e w i l l b e more e f f i c i e n t i n t e a r i n g a n e l e c t r o n away from t h e f o i l t h a n w i l l a s i n g l e p r o t o n , and t h e r e f o r e w i l l enhance t h e n e u t r a l c h a r g e f r a c t i o n . The wake a t t r a c t i o n o n l y e x t e n d s o v e r a 30° a n g l e behind t h e f i r s t : p r o t o n [ 4 1 , s o a n H2 -!- i o n e n t e r i n g t h e f o i l b r o a d s i d e w i l l b r e a k up and emerge a s i n d e p e n d e n t atoms. Thet r i a n g u l a r H3
+
w i l l have a l a r g e r p r o b a b i l i t y o f h a v i n g two of i t s p r o t o n s h i t t h e f o i l c o l l i n e a r l y and t h e r e f o r e shows a n even l a r g e r n e u t r a l c h a r g e f r a c t i o n t h a n H2. A s+
o b s e r v e d i n ion-atom c o l l i s i o n s [5] t h e r e l a t i v e l e v e l p o p u l a t i o n f a l l s o f f a s nP w i t h p s l i g h t l y l e s s t h a n -3 ( -4.0 f o r
25 keV/amu, -3.6 f o r 100 keV/amu ) and a p p r o a c h i n g -3 a t l a r g e v e l o c i t i e s .
The t a b l e p r e s e n t s some t y p i c a l d a t a f o r oxygen. The o v e r a l l u n c e r t a i n t y r e l a t e d t o t h e numbers o f t h e l a s t two columns i s a p p r o x i m a t e l y 5%. The r e l a t i v e change o f i n t e n s i t y f o r d i f f e r e n t l i n e s of t h e same c h a r g e s t a t e i s a l m o s t t h e ' s a m e , a n d , e s p e c i a l l y f o r O I V , t h e same e f f e c t i s ,found a s f o r hydrogen. Two c o m p l i c a t i n g c i r c u m s t a h c e s o b s c u r e t h e p i c t u r e f o r t h i s p r o j e c t i l e . One i s t h e much lower v e l o c i t y , t h e o t h e r t h e f a c t t h a t t h e oxygen i o n s a r e m u l t i p l y c h a r g e d when t h e y l e a v e t h e f o i l
[61 and t h e r e f o r e need t o p i c k up s e v e r a l e l e c t r o n s t o end up i n t h e c h a r g e s t a t e s measured.
O I V 3p
I
l - O 6e x c i t e d .
1
r a t i o o f s i g n a l produced by O2+
One o f u s ( N ) i s g r a t e f u l t o t h e Research I n s t i t u t e f o r P h y s i c s f o r t h e h o s p i t a l i t y h e enjoyed d u r i n g h i s s t a y , a s w e l l a s f o r f i n a n c i a l s u p p o r t from t h e Nordic A c c e l e r a t o r Committee.
l e v e l
O I I 3d' O I 1 4 f 1 0 1 1 4f
REFERENCES
111 L. Lundin, B. Engman, J. H i l k e and I.
M a r t i n s o n , P h y s i c a S c r i p t a
8 ,
274 ( 1 9 7 3 ) .1 2 1 B.T. M e g g i t t , K.G. H a r r i s o n and M.W.
Lucas, J. Phys. B,
6 ,
L362 ( 1 9 7 3 ) - 131 2. Vager and D.S. Gemmell, Phys. Rev.L e t t . , 1352 ( 1 9 7 6 ) .
[ 4 ] D.H. J a k u b a s s a , J . Phys. C,
10,
4491 ( 1 9 7 7 ) .[ 5 ] B. Andresen, K. J e n s e n , N.B. P e t e r s e n and E. Veje, Phys. Rev. A,
E,
1469(1977).
163 E. V e j e , Phys. Rev. A ,
14,
2077 ( 1 9 7 6 ) . ando*.
beams a t100 keV
- 1.04 1.00 0.99
155 keV
0.89 0.91 0.93