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Submitted on 1 Jan 1979
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CN MOLECULAR BANDS IN A FREE BURNING METAL ELECTRODES ARC
G. Buchet, R. Haug, J. Maftoul
To cite this version:
G. Buchet, R. Haug, J. Maftoul. CN MOLECULAR BANDS IN A FREE BURNING METAL ELECTRODES ARC. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-327-C7-328.
�10.1051/jphyscol:19797161�. �jpa-00219137�
JOURNAL DE PHYSIQUE CoZZoque C7, suppl6ment a u n07, Tome 40, J u i Z Z e t 1979, page C7- 327
CN MOLECULAR BANDS IN A FREE BURNIbS METAL ELECTRODES ARC
G. Buchet, R. Haug and J. Maftoul.
L a b o r a t o i r e de P h y s i q u e d e s DQcharges ER 114 d u C.U.R.S., EcoZe S u p Q r i e u r e d l E Z e c t r i c i t Q , P l a t e a u d u MouZon - 91190 G i f - S w - Y v e t t e , F~ance.
I . I n t r o d u c t i o n i n c r e a s e s which diminishing a r c v o l t a g e and i n v e r - The behavior of t h e a r c , t h e e l e c t r o d e e r o s i o n s e l y on f i g . 3. Exploring t h e a r c column i n a i r with and t h e s t a b i l i t y depend on t h e m a t e r i a l of t h e i n d u s t r i a l copper e l e c t r o d e s , t h e v i o l e t system of e l e c t r o d e s used and on t h e ambient gas. The know- molecular bands of CN i n t h e r e g i o n 3850-4216 A was ledge of t h e a r c spectrum i s an important t o o l i n found.
o r d e r t o e x p l a i n t h e above mentioned phenomena. We B~ 1'
+x2 Z+ A v = O , A v = l
have shown t h a t a temporal c o r r e l a t i o n e x i s t s b e t - TO s o l v e t h e problem of t h e o r i g i n of CN, t h e e l e c - ween s p e c t r a l l i n e s i n t e n s i t y and a r c v o l t a g e f l u c - t r o d e s were r e p l a c e d by u l t r a p u r e copper e l e c t r o d e s t u a t i o n s [ I ] . The molecular bands having a p o s i t i v e (99,995 %). The molecular bands were s t i l l v i s i b l e c o r r e l a t i o n c o e f f i c i e n t a r e i d e n t i f i e d h e r e a s w e l l ( f i g . 4 ) . When a r c was burning i n a i r , b u t they a s the o r i g i n of t h e r e s p o n s i b l e r a d i c a l . disappeared ( f o r b o t h types of e l e c t r o d e s ) when a i r 2. Experimental Techniques and R e s u l t s
The spectrum of f r e e burning a r c s i n a i r , N 2' a i r + C02 and Ar+ O2 mixtures h a s been s t u d i e d . The e l e c t r o d e s were of d i f f e r e n t p u r i t y grades of copper. The experimental s e t r ~ i s shown i n f i g . I The v o l t a g e used was 250 V with a c u r r e n t of 1.,5 A , and a gap s p a c i n g of 2-3 mm. Under t h e s e c o n d i t i o n s t h e a r c i s r a t h e r s t a b l e and t h e spectrum can be
was r e p l a c e d by mixtures of Arand O2 (both of 99,995 % p u r i t y ) a s i t i s c l e a r from f i g . 5 .
For a r c s burning i n an atmosphere of N2(99,995%) t h e molecular bands of n i t r o g e n a r e so i n t e n s e t h a t i t i s impossible t o d e t e c t t h e molecular bands,of
a i r burning, CN. I t i s i n t e r e s t i n g t o remark t h a t i n a n Y a r c w i t h small c u r r e n t s ( < 3 A ) t h e molecular bands of n i t r o g e n a r e n o t observed. For an a r c burning i n C@
2
recorded f o r a r e l a t i v e l y long p e r i o d of time e n r i c h e d a i r we observed t h a t t h e CN molecular bands ( ,, 30 ) which allows the same wavelength inter- i n t e n s i t y i n c r e a s e d c o n s i d e r a b l y (500-1000 t i m e s ) .
to be several times. T~~ reproduc.bi- This f a c t a d d i t i o n a l l y proves an atmospheric o r i g i n l i t y of the spectra is satisfactory. ~ h ~ photomul- of CN. The measurements of t h e CN molecular bands t i p l i e r c u r r e n t and t h e a r c v o l t a g e a r e synchro- i n t e n s i t y allow t o e s t i m a t e t h e C02-concentration.
nously sampled with a frequency i n t h e 1 KMz-I MHz I t a p p e a r s 1 2 1 t h a t i k l t h e system C-0-N t h e range and recorded i n a wave memory r e c o r d e r c o n c e n t r a t i o n of CN r a d i c a l i n c r e a s e s w i t h i n c r e a - ( 2 ,024 samples). The samples are then displayed s i n g gas temperature. For temperatures of T > 6000°K on an X - ~ o s c ~ ~ l o s c o p e ( x f o r l i g h t and Y f o r vol- i n t h e f r e e burning a r c i n a i r o n l y t h r e e types of t a g e ) . The s e t of p o i n t s s t a t i s t i c a l l y c h a r a c t e r i z e and atoms exist ' CN*
N yO,
t h e mentionned c o r r e l a t i o n . Fig. 2 r e f e r s t o a 3 . Conclusions Copper l i n e (5153 A ) - f i g . 3 r e f e r s t o t h e head
The experiments show t h a t r a d i c a l s of CN found of molecular band (3883 A) f o r a f r e e burning a r c
i n t h e a r c burning i n a i r have an atmospheric o r i - i n a i r . The comparison between f i g s 2 and 3 shows
g i n . When metal vapour emission ceases t h e a r c vol- t h a t t h e average s l o p e s of t h e c l o u d s of p o i n t s a r e t a g e increases due t o decreasing c o n d u c t i v i t y and o p p o s i t e . p r e c i s e l y , on f i g . 2 t h e l i g h t i n t e n s i t y synchronously t h e CN band i n t e n s i t y i n c r e a s e s .
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19797161
M.G. Drouet, R. Haug, M. Goldman,
31th Annual Gaseous Electronics Conference, Buffalo, New York.
J. Amouroux,
Private Communication.
Fig. 1 Experimental setup
M - mirror,^ - quartz window In - inlet for gas injection B - box, S - spectrometer
PM - photomultiplier, Rg - recorder
Fig. 2 Correlation between light intensity
Fig. 3 Correlation between light intensity ( h = 3884 - head of CN molecular band) and arc voltage.
Fig. 4 .Spectrum of an arc burning in air.
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