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Submitted on 1 Jan 1979
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FORMATION OF K2 (A’ Σ +u) MOLECULES CAUSED BY K(4P) ATOMS IN POTASSIUM
DISCHARGE
V. Lukashenko
To cite this version:
V. Lukashenko. FORMATION OF K2 (A’
Σ+u) MOLECULES CAUSED BY K(4P) ATOMS IN POTASSIUM DISCHARGE. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-113-C7-114.
�10.1051/jphyscol:1979756�. �jpa-00219462�
JOURNAL DE PHYSIQUE CoZZoque C7, suppZ6ment au n07, Tome 40, JuiZZet 1979, page C> 113
FORMATIW OF K2 (A' C
3
MOLECULES CAUSED BY K(4P) ATOMS W WTASSRlM DISCHARGE V.I. Lukashenko,I n s t i t u t e o f EZectrodynamics, Kiev 252057, U. S. S.R.
An a n a l y s i s of t h e g e n e r a t i o n mechanisms of t h e e l e c t r o n - e x c i t e d potassium molecu- l e s K ~ ( A ' E ): made i n paper
[I]
h a s revea- l e d a high e f f i c i e n c y of the r e a c t i o nAccording t o [2] t h e c o l l i s i o n a l e x c i t a t i - on t r a n s f e r from atom t o molecule may be considerable under some c o n d i t i o n s
I n p r e s e n t work t h e r o l e of abovementioned p r o c e s s e s i n a discharge potassium plasma a t medium p r e s s u r e s p = (0. I + I . O ) t o r r was i n v e s t i g a t e d and the c r o s s - s e c t i o n s qI and q2 f o r r e a c t i o n s ( I ) and (2) were e s t i m a t e d by r a t h e r simple method.
Each of t h e s e r e a c t i o n s r e s u l t s i n appea- rance of an e l e c t r o n - e x c i t e d molecule i n exchange f o r a r e s o n a n t e x c i t e d atom. The p o s s i b i l i t y of such ffconversionff was c l e - a r l y demonstrated by following experiment.
A c e l l with potassium vapour w a s r a d i a t e d by t h e r e s o n a n t quanta f l u x from t h e sour- ce of s p e c i a l c o n s t r a c t i o n d e s c r i b e d pre- v i o u s l y i n
[I].
The t o t a l number of quan- t a Q absorbed by t h e c e l l and t h e molecu- lar emission f l u x F (number of quanta emi- t t e d by t h e c e l l f o r second i n a l l d i r e c -t i o n s w i t h i n t h e
-
X'Z+ band system) gwere measured. The obtained experimental dependences of F upon p a r e r e p r e s e n t e d i n F i g . 1 f o r two magnitudes of Q.
8
p , t o r r Fig. I.
The f a c t t h a t a t p r e s s u r e s p 3 0 , 3 t o r r t h e magnitude of F exceeds t h e h a l f of Q (see Fig.1) t e s t i f i e s t o t h e high e f f i c i e n c y of t h e frconversion" of t h e K(4P) atoms i n t o
f +
t h e e l e c t r o n - e x c i t e d molecules K2(A x u ) . The s i m i l a r p i c t u r e should be observed i n discharge plasma, were t h e K(4P) atoms a r e generated by e l e c t r o n Impacts. To elimina- t e t h e i n f l u e n c e of e l e c t r o n s upon gene- r a t i o n and d e a c t i v a t i o n of t h e K2(A
'z:)
molecules very low discharge c u r r e n t s ( I + 2) mA were used. Under t h e s e c o n d i t i o n s
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979756
i n t e g r a t e d over wavelength i n t e n s i t i e s of molecular band Ib and r e s o n a n t l i n e s I1 can be e x p r e s s e d by
Combination of ( 3 ) and ( 4 ) g i v e s us t h e e x p r e s s i o n f o r e f f e c t i v e "conversion"
c r o s s - s e c t i o n
Where Na and Nm a r e t h e d e n s i t i e s of non- e x c i t e d potassium atoms and dimers, r e s p e - c t i v e l y [3), N* i s t h e c o n c e n t r a t i o n of t h e atoms K(4P), summerized o v e r t h e doub- l e t s t r u c t u r e components, V i s t h e r e l a t i - ve thermal v e l o c i t y of t h e c o l l i d i n g p a r - t i c l e s (V2/VI=0.87), Z i s t h e e f f e c t i v e l i f e t i m e of potassium atom i n 4P s t a t e . Experimental dependence of t h e magnitude Ib/I1 upon Na i s d e p i c t e d i n F i g . 2 ( a ) .
I 2 3 5 7 1 0
N a . I O - ' ~ , cm-3 Fig. 2.
As can be s e e n , f o r Na 6 . 1 0 ' ~ t h e band becomes b r i g h t e r t h a n t h e r e s o n a n t l i n e s and, c o n s e q u e n t l y , t h e molecular emi- s s i o n becomes t h e main channel of t h e r a - d i a t i o n l o s s from t h e d i s c h a r g e .
It i s c l e a r , t h a t a t low p r e s s u r e , where Nm/Na i s s m a l l , qe i s e q u a l t o qI and t h e n it should i n c r e a s e w i t h p r e s s u r e due t o t h e c o n t r i b u t i o n o f t h e p r o c e s s ( 2 ) .
Using t h e d a t a of F i g . 2 ( a ) and t h e value of 't f o r a c y l i n d r i c a l plasma column [41 i t i s e a s y t o c a l c u l a t e t h e dependence o f q, upon Na. The r e s u l t of c a i c u l a t i o n i s g i v e n i n F i g . 2 ( b ) . I n accordance w i t h t h i s f i g u r e t h e c r o s s - s e c t i o n f o r recombi- n a t i o n qI i s e q u a l t o 1 . 3 - 1 0 -16cm2, t h a t i s i n r a t h e r good agreement w i t h t h e v a l u e q1 = 1. 6.10-I6 cm 2
,
o b t a i n e d i n p a p e r[I].
D i f f e r e n c e s (4,- q I ) i n t h e r a n g e of Na", 5 . 1 0 ' ~ a l l o w u s t o e s t i m a t e t h e c r o s s
s e c t i o n f o r e x c i t a t i o n t r a n s f e r q2.
A s f o l l o w s from t h e d a t a of F i g . 2 ( b ) q2 a 2.10-I4 cm 2
.
I n c o n c l u s i o n it should be n o t e d , t o de- termine t h e c r o s s - s e c t i o n s qI and q2 by d e s c r i b e d method it i s r e q u i r e d t o measure t h e r e l a t i v e i n t e n s i t i e s of molecular band and r e s o n a n t l i n e s o n l y .
References
.
I.Yu.P.Korchevoi,V.I.Lukashenko, S.N.Luka- shenko, Z h . E x p . T e o r . F i z . 2 , 846 (1978).
2.L.K.Lam e t a l . , J.Chem.Phys., 68, 3553 (1978)
3. A.N.Nesmeyanov, Vapour P r e s s u r e of E l e - ments (Academic, New Y o r k , 1963).
4.Yu.P.Korchevoi, S.N.Lukashenko, O p t i c a and S p e c t r o s c . ,
