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RELATIVE LEVEL EXCITATION IN BEAM-FOIL EXCITED Li AND Be
J. Bromander, S. Hultberg, B. Jelenkovik, L. Liljeby, S. Mannervik, E. Veje
To cite this version:
J. Bromander, S. Hultberg, B. Jelenkovik, L. Liljeby, S. Mannervik, et al.. RELATIVE LEVEL
EXCITATION IN BEAM-FOIL EXCITED Li AND Be. Journal de Physique Colloques, 1979, 40
(C1), pp.C1-259-C1-260. �10.1051/jphyscol:1979154�. �jpa-00218434�
JOURNAL DE PHYSIQUE Colloque C1, supplkment au n O 2, Tome 40, fgvrier 1979, page Cl-259
RELATIVE LEVEL EXCITATION I N BEAM-FOIL EXCITED L i AND Be
J . Bromander, S. H u l t b e r g , B. J e l e n k o v i b , L. L i l j e b y , S. Mannervik and E. Ve)e Research I n s t i t u t e f o r P h y s i c s , ~ o s l a g s v a g e n 100, S-104 05 Stockholm 50, Sweden
~Bsumci. Nous avons CtudiB d e s s p e c t r e s beam-foil d e Li e t Be d a n s l a domaine 200-550 nm d e l o n g u e u r d ' o n d e s . Les p o p u l a t i o n s r e l a t i v e s d e s d i f f s r e n t s n i y aux
5
d e Rydberg d e l a m b e s g r i e d e t e r m e s d s c r o i s s e n t un peu p l u s rapidement q u e n,
c o m e on a pu c o n s t a t e r d a n s l e s c o l l i s i o n s e n t r e i o n s e t atomes s o u m i s i d e s c o n d i t i o n s d e c o l l i s i o n s s i m p l e s . La p o p u l a t i o n r e l a t i v e d e s niveaux a y a n t l e m&e numero q u a n t i q u e p r i n c i p a l c r o r t quand l e s n i v e a u x c h a n g e n t d e s v e r s p , d 4 c r o f t d e p v e r s d , e t c r o r t e n c o r e d e d v e r s g.A b s t r a c t . We have s t u d i e d t h e o p t i c a l beam-foil s p e c t r a o f L i and Be i n t h e wavelength r e g i o n 200-550 nm. The r e l a t i v e popula_tion f o r d i f f e r e n t Rydberg l e v e l s of t h e same t e r m s e r i e s d e c r e a s e s somewhat f a s t e r t h a n n
,
a s i s a l s o observed i n ion-atom e n c o u n t e r s under s i n g l e c o l l i s i o n c o n d i t i o n s . The r e l a t i v e l e v e l p o p u l a t i o n f o r l e v e l s o f t h e same p r i n c i p a l quantum number i n c r e a s e s from s t o p l e v e l s , d e c r e a s e s from p t o d l and i n c r e a s e s a g a i n from d t o g l e v e l s .We have s t u d i e d t h e o p t i c a l beam- f o i l s p e c t r a o f L i a t 210 keV and o f B e a t 156 keV, 256 keV and 348 keV, i n t h e
wavelength r e g i o n 200-550 nm. The p u r p o s e s were ( i l t o measure r e l a t i v e p o p u l a t i o n s of welL e s t a b l i s h e d e x c i t e d l e v e l s i n L i I , L i I I and B e I I , ( i i ) t o remeasure some e a r l i e r o b s e r v e d s p e c t r a l l i n e s w i t h
improved r e s o l u t i o n and (iii) t o s e a r c h f o r p o s s i b l e new s p e c t r a l l i n e s . We r e p o r t h e r e t h e r e l a t i v e p o p u l a t i o n d a t a , which y i e l d i n f o r m a t i o n a b o u t p r o j e c t i l e - s o l i d
i n t e r a c t i o n s
.
The measurements were c a r r i e d o u t a t t h e 400 kV heavy i o n a c c e l e r a t o r a t t h e Research I n s t i t u t e f o r P h y s i c s i n Stockholm
[ I I . A s c a n n i n g monochromator o b s e r v e d photons e m i t t e d immediately b e h i n d t h e f o i l s , and t h e monochromator was quantum e f f i c i e n c y c a l i b r a t e d by means o f a q u a r t z - h a l o g e n lamp s t a n d a r d o f s p e c t r a l r a d i a n c e i n c o m b i n a t i o n w i t h a BaSOg s c r e e n E2J. The r e l a t i v e t e r m p o p u l a t i o n N of l e v e l j was d e t e r m i n e d from t h e r e l a t i o n [ 3 ] j
N = S(A)/K(X) - A j f
j (1)
where S ( A ) i s t h e s i g n a l o f t h e o p t i c a l t r a n s i t i o n from l e v e l j t o l e v e l f , a t t h e wavelength A , K ( A ) i s t h e quantum
e f f i c i e n c y o f t h e o p t i c a l d e t e c t i o n s y s t e m , and A j f i s t h e t r a n s i t i o n p r o b a b i l i t y f o r t h e t r a n s i t i o n s t u d i e d .
I n F i g . 1 a r e shown t h e r e s u l t a n t r e l a t i v e l e v e l p o p u l a t i o n d a t a a s f u n c t i o n s of t h e e f f e c t i v e quantum number, f o r v a r i o u s Rydberg term s e r i e s i n L i I , L i I I and B e I I , i n a log-log p l o t . We n o t e t h a t d a t a f o r t e r m s o f t h e same s e r i e s c a n be c o n n e c t e d by a s t r a i g h t l i n e . T h i s i s i n agreement
210 keV
Bell n12f 156 key-38 keV
Bell n s ' ~ 156 keV -3Ui kev
I
3
EFFECTIVE IIUANTUM NUMBER. no
F i g . 1
-
R e l a t i v e l e v e l p o p u l a t i o n s a s f u n c t i o n s o f t h e e f f e c t i v e quantum number.Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979154
c
1-260 JOURNAL DE PHYSIWEw i t h e a r l i e r f i n d i n g s f o r beam-foil e x c i t a t i o n s 131 and a l s o f o r ion-atom c o l l i s i o n s [41. I t may a l s o have an
e x p l a n a t i o n s i m i l a r t o t h e o n e a d e q u a t e f o r ion-atom c o l l i s i o n s [ 4 ] , namely, t h a t t h e e x c i t a t i o n p r o b a b i l i t y i s d e t e r m i n e d p r i m a r i l y from t h e a m p l i t u d e o f t h e f i n a l s t a t e wave f u n c t i o n i n t h e v i c i n i t y o f t h e n u c l e u s .
The r e l a t i v e p o p u l a t i o n r e s u l t s a r e i n F i g . 2 p l o t t e d v e r s u s t h e o r b i t a l a n g u l a r momentum quantum number. Data f o r l e v e l s o f t h e same p r i n c i p a l quantum number a r e c o n n e c t e d by broken l i n e s . W e n o t e t h e s t r o n g p o p u l a t i o n o f p l e v e l s , and mention t h a t t h e L i r e s u l t s on r e l a t i v e s c a l e s f i t e a r l i e r measurements [31 done w i t h a
p r o j e c t i l e e n e r g y o f 40 keV.
The r e s u l t s i n F i g . 2
s u b s t a n t i a t e e a r l i e r f i n d i n g s [ 3 ] f 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 s t h r o u g h f l e v e l s . F u r t h e r m o r e , t h e p o p u l a t i o n o f t h e o n l y g
l e v e l o b s e r v e d ( 8 g 2 G i n B e I I ) seems t o b e l a r g e r t h a n t h a t o f t h e c o r r e s p o n d i n g f l e v e l ( we were u n a b l e t o o b s e r v e t h e p o p u l a t i o n o f t h e 8 f 2~ l e v e l i n B e I I . The
datum p o i n t shown i n a b r a c k e t f o r t h e 8f l e v e l i n F i g . 2 was o b t a i n e d from
e x t r a p o l a t i n g t h e nf s e r i e s d a t a i n F i g . 1) I t h a s r e c e n t l y been found a l s o i n MgII t h a t t h e g l e v e l p o p u l a t i o n i s b i g g e r t h a n t h a t of t h e c o r r e s p o n d i n g f l e v e l [51 i n agreement w i t h t h e f i n d i n g f o r B e I I .
We c o n c l u d e t h a t 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 o r l e v e l s of t h e same p r i n c i p a l quantum number i n c r e a s e s from s t o p , d e c r e a s e s from p t o d l and i n c r e a s e s a g a i n when g o i n g from d t o g l e v e l s . T h i s i s d i f f e r e n t from t h e s y s t e m a t i c s o f ion- atom c o l l i s i o n s , which show a p e a k i n g a t d l e v e l s and a low p o p u l a t i o n of f and g l e v e l s 161.
One of t h e a u t h o r s (EV) 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 he enjoyed d u r i n g h i s s t a y , a s w e l l as 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.
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