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THE RELATIVE CONTRIBUTION OF ASSOCIATIVE IONIZATION AND
PHOTOIONIZATION IN XENON PRECURSORS
M. Vasil’Ev, T. Zhikhareva, G.K. Tumakaev
To cite this version:
M. Vasil’Ev, T. Zhikhareva, G.K. Tumakaev. THE RELATIVE CONTRIBUTION OF ASSOCIA-
TIVE IONIZATION AND PHOTOIONIZATION IN XENON PRECURSORS. Journal de Physique
Colloques, 1979, 40 (C7), pp.C7-101-C7-102. �10.1051/jphyscol:1979750�. �jpa-00219456�
JOURNAL DE PHYSIQUE Colloque C7, suppzgment au no?, Tome 40, JuiZZet 1979, page C7- 101
THE RELATIVE CONTRIBUTION OF ASSOCIATIVE IONIZATION AND PHOTOIONIZAflON XENON PRECURSORS
M.G. Vasil'ev, T.V. Zhikhareva and G.K. Tumakaev.
I o f f e Physicotechnical I n s t i t u t e , Academy o f Sciences, Leningrad, U.S.S.R.
A b s t r a c t . The k i n e t i c s of xenon e x c i t a t i o n c o l l i s i o n s w i t h atoms, a l s o tile chances i n and i o n i z a t i o n and of t h e e l e c t r o n gas h e a -
tile electron gas energy involved in the t i n g ahead of t h e shock f r o n t were s t u d i e d
t h e o r e t i c a l l y f a r t h e &Pack number r a n g e 1 4 p i l o t o i o n i z a t i o n , a s s o c i a t i v e i o n l z a t i o n t o 20 and i i l i t i o l p r e s s u r e p = 5 slu~ Hg.The and d i s s o c i a t i v e r e c o n b i n a t i o n p r o c e s s e s . i o n i z a t i o n k i n e t i c s of xenon atoins was
found t o d i f f e r s u b s t a n t i a l l y f r o u t h a t of The r o l e of v a r i o u s Bidberg s t a t e s of argon. I n t h i s c a s e one should t a k e siriiul- &enon atoms p a r t i c i p a t i n g i n tile a s s o c i a - t a n e o u s l y l n t o account b o t h a s s o c i a t i v e
l o l l i z a t i o n a a p h o t o i o n i z a t i o n , t h e l a t t e r t i v e l o n l z a t i o l l r e a c t i o n /4/ h a s a l s o been becouiing predominant i n t h e chkrged p a - t i c - s t u d i e d . S i n c e tile o s c i l l a t ~ r s t r e n g t k ~ s l e p r o d u c t i o n a n xenon w i t h i n c r e a s i n g f o r t h e t r a n s i t i o n s i n t o t h e s e s t a t e s s t r e n g t l i of t h e i n c i d e n t shock. The t h e o r e -
t i c a l p r e d i c t i o n s f o r t h e e l e c t r o n d e n s i t y d i f f e r s u b s t a n t i a l l y r r o u one a n o t i l e r , t h e a r e oompared w i t h e x p e r i m e n t a l v a l u e s . c o n t r i b u t i o n of t h e atoins t o t h e o l ~ a r g e d
A s h a s been e s t a b l i s h e d e a r l i e r //l,;?/, p a r t i c l e p r o d u c t i o n i s n o t t h e same. The p h o t o i o n i z a t i o n i n t h e a r g o n p r e c u r s o r s l a r g e s t and a l m o s t e q u a l c o n t r i b u t i o n s co-
4 C
c a n n o t aocount l o r u r p e r l m e n t a l v a l u e s of me from atoms i n t h e 6d
L1ili
and 5d't h e e l e c t r o n d e n s i t y ahead of a shock even
id;];)
s t a t e s , t h e s u l a l l e s t one b e i n g d u e when t h e r e f l e c t i o n of l i n e and continuum t o t h e 7d[($I:
s t a t e . Tile d i f f e r e n c e r a d i a t i o n from t h c t u b e w a l l s IS I n c l u d e d . i n t h e m o l e c u l a r i o n d e n s i t i e s f o r t h e s e The dominant neckanism of charged p a r t i c l e c a s e s i s a f a c t o r of + lQ3.p r o d u c t i o n i n a r g o n i s a s s o c i a t i v e i o n i z a - The r e s u l t i n g s y s t e u of d i l f e r e n t i a l t i o n of t h o Uolner-type /5/. The p r e s e n t e q u a t i o n s U e s c r i b i n g t h e k i n e t i c s of e l e c t - work d e a l s w i t h a s t u d y O f t h e k i n e t i c s of r o n g a s excitation, i o n i z a t i o n and h e a t i n g fundamental p r o c e s s e s i n t h e xenon y r e c u r - w i t h asymp'totic b o u m a r y c o n d i t i o n s \vas s o r s w i t h t h e p u r p o s e of d e t e r m i n i n g t h e
predominant machanism of i o n i z a t i o n . 'i'he r a d i a t i v e and ; o l l i s i o n a l p r o c e s s e s c o n s i - d e r e d xenon atoms I n r e s o n a n c e and h i g h l y e x c i t e d a t a t e s i n cha p h o t o e x c i t a t i o n of ground s t a t e atoms and t h e i r r a d i a t i v e and oascade t r a n s i t i o n r e l a x a t i o n t h e t h e ground s t a t e ; ( 2 ) P h o t o i o n i z a t i o n of atoms from t h e ground and r e s o n a n c e s t a t e s ) ; (5) E x c i t a t i o n of atoms f r o u t h e ground i n t o r e s o n a n c e s t a t e s and t h e p r o c e s s e s of t h e i r de-exc i t a t i o n and i o n i z a t i o n by e l e - c t r o n i m p a c t ; ( 4 ) A s s o c i a t i v e i o n i z a t i o n i n v o l v i n g an atom i n a h i g h l y e x c i t e d Bid- b e r g s t a t e
XZ;
+ Xe + Xe:+ e and d i - s s o c i a t i v e r e c o m b i n a t i o n ; ( 5 ) l o n i c conver- s i o n %e+
+ Xe + $2 2 % e l + XQ,iihen c o n s t r u c t i n g t h e energy b a l a n c e e q u a t i o n f o r t h e e l e c t r o n gas, we i n c l u d e d , a p a r t from e l a s t i c and i n e l a s t i c e l e c t r o n
s o l v e d n u i n e r i c a l l y by t h e ilunye-kutta ule- thod.
The r e s u l t s of elre computations show t h a t w h i l e t h e e x c i t a t i o n k i n e t i c s of t h e i n e r t g a s e s a r e t h e same, t i l e i o n i z a t i o n k i n e t i c s of sellon J i 9 f e r s ruariiedly f r o u t h a t of argon. ittiis i s due p r i r i a r i l y t o t h e h i g h p l i o t o i o n i z a t i o n c r o s s s e c t i o n of e x c i t e 4 xenon u t o u s wirich exceeds by about 20 t i m e s t h a t of argon. The p i ~ o t o i o n i z a t i - on c r o s s s e c t i o n of tire 6 s
[li]; ,
r e s o - nance l e v e l was c a l c u l a t e d b y the ~ietilocl of Uurgess-Seaton /5/, i t s v a l u e a t t h e t h r e s l l o l d b e i n g 3.6 8 lCv'18 c u 2.
Fig.1 p r e s e n t s i o n i z a t i o n
rates.
v s .dis- t a n c e rrom tile s i ~ o c i i f r o n t i n u n i t s of tu- be r a d i u s ( R 5 cni). Ln c o n t r a s t t o arbon, where t h e p r o d d c t i o n o f charged p a r t i c l e s i s clet ermined p r edoiilinalltly by a s s o c i a t i v e i o n i z a t i o n ~ v i l i l e clle p l ~ o t o i o n i z a t i o n pro-Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979750
Fig.1. ~ o n i z a t i o n r a t e p r o f i l e s ( ~ m - ~ s ' l ) . S o l i d curve: e x c i t e d s t a t e photoio- n i z a t i o n r a t e ; Dashed curve: asso- c i a t i v e i o n i z a t i o n r a t e .
1: M-14 without r e f l e c t i o n . 2: ~ 5 2 0 w i t h o u t r e f l e c t i o n . 3: Y-20 w i t h r e f l e c t i o n .
~ i g . 2 . E l e c t r o n d e n s i t y p r o f i l e s ( c d 3 )
.
S o l i d curves: t h e o r y f o r t h e c a s e s i n t h e preceding f i g u r e ;
Dashed curves: d a t a obtained by mic- rowave i n t e r f e r o m e t r y /6/.
c e a s e s a r e n e g l i g i b l e , i n xenofi a t f 1 t h e probabilities of p h o t o i o n i z a t i o n ( ~ h ) and a s s o c i a t i v e i o n i l r e t i o n (As) become c o r p a r a b l e a l r e a d y a t M ~ 1 4 , t h e ( ~ h ) r a t e e r . oeeding t h e ( A S ) r a t e i n t h e immediate v i - o i n i f y of t h e shock f r o n t .
The c o m p e t i t i v e r o l e of t h e photoionisa- Bfon of e x c i t e d s t a t e s eompared w i t h t h e
@ e ~ e s t 3 of a s s o c i a t i v e i o n i z a t i o n i n a r e a s -
e s subs t a n t i a l l y with i n c r e a s i n g Mach num- b e r anci when t a k i n g i n t o account t h e r e f - l e c t i o n of r a d i a t i o n from t h e w a l l s . Ande- ed, even without t h e i n c l u s i o n of r e f l e c t i - on, (ph) exceeds (AS) by an o r d e r of magni- t u d e near t h e b l f r o n t a t k320, These ~ ~ ~ ~ p r o c e s s e s become comparable h e r e a t a much l a r g e r d i s t a n c e from t h e f r o n t ( #&lo) t h a n i s t h e c a s e a t ~ ~ 1 4 , Taking t h e r e f - l e c t i o n i n t o account i n c r e a s e s s u b s t a n t i - a l l y t h e r o l e of t h e e x c i t e d s t a t e photo- i o n i z a t i o n . As a r e s u l t , t h e p h o t o i o n i z a t i - on p r o c e s s becoues predominant throu&lout t h e range of f~ considered.
Note t h a t a s t d e p h o t o i o n i z a t i o n e f f i c i - ency i n c r e a s e s , t h e e f f i c i e n c y of t h e ato- mic-to-molecular i o n conversion a s w e l l a s of t h e d i s s o c i a t i v e recombination p r o c e s s w i l l l i k e w i s e i n c r e a s e accordingly. Indeed, a t ~ " 2 0 t h e i o n conversion r a t e throughout t h e range of
9
considered exceeds t h e as- s o c i a t i v e i o n i z a t i o n r a t e i f t h e r a d i a t i o n r e f l e c t i o n i s c o n s i d e r e d , so t h a t under t h e s e c o n d i t i o n s t h e molecular i o n s s i ~ o u l d f oru p r i n a r i l y by way of conversion of ato- mic i o n s r a t h e r t h a n i n the course of t h ea s s o c i a t i v e i o n i z a t i o n process a s was t h e c a s e f o r 61514.
Fig.2 shows the t h e o r e t i c a l and experi- mental p r o f i l e s of e l e c t r o n u e n s i t y . A con- p a r i s o n of t h e r e s u l t s i n d i c a t e s a s a t i s - f a c t o r y agreement between t h e experimental and t h e o r e t i c a l d a t a and a q u a l i t a t i v e l y good f i t of t h e c a l c u l a t e d e l e c t r o n d e n s i - t i e s f o r bile c a s e of r a d i a t i o n - r e f l e c t i n g w a l l s t o t h e experimental dependence on
8 -
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