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HAL Id: jpa-00219377

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Submitted on 1 Jan 1979

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IONIZATION AND ATTACHMENT IN WATER VAPOUR AND AMMONIA

A. Risbud, M.S. Naidu

To cite this version:

A. Risbud, M.S. Naidu. IONIZATION AND ATTACHMENT IN WATER VAPOUR AND AM- MONIA. Journal de Physique Colloques, 1979, 40 (C7), pp.C7-77-C7-78. �10.1051/jphyscol:1979738�.

�jpa-00219377�

(2)

JOURNAL DE PHYSIQUE Colloque C7, suppZ&ment ou n07, Tome

40,

J u i l l e t

1979,

page C 7 -

7 7

IONIZATION AND ATTACHMENT IN WATER VAPOUR AND AMMONIA

A.V. Risbud and M.S. ~ a i d u * .

.Indian I n s t i t u t e o f Science, Banga Lore, India.

Presently w i t h Eindhoven Universitg o f Technology, EEg, Group EHO, Eindhoven, The Netherlands.

I n t r o d u c t i o n . E l e c t r o n attachment i n water vapour h a s n o t been e x t e n s i v e l y s t u d i e d a s i n o t h e r g a s e s , such a s , oxygen and i t s compounds, There a r e d i s - c r e p a n c i e s between t h e e x i s t i n g d a t a ( 1 - 5 ) . The r e s u l t s of P a r r and Moruzzi ( 5 ) a r e h i g h e r t h a n t h o s e o f Kuffel ( 1 ) and Ryzko ( 4 ) b u t a r e lower t h a n t h o s e of Prasad and Craggs ( 2 ) . Regarding t h e p r o c e s s o f attachment, while Kuffel ( 1 ) observed it t o be a three-body p r o c e s s a t low E/N. Moruzzi and Phelps ( 6 ) d i d n o t s e e any attachment f o r E/N

> 33 Td. Like wise,

a

of Prasad and Craggs ( 2 ) and

- N

Ryzko ( 4 ) a l s o d i f f e r .

Extreme c a r e was taken i n p u r i f i c a t i o n and d r y i n g o f t h e g a s samples a s suggested by e a r l i e r workers ( 5 ) . water vapour used was from s p e c i a l l y prepared t r i p l y d i s t i l l e d d e i o n i z e d w a t e r , while ammonia used was purifieC? by f r a c t i o n a l d i s t i l l a t i o n and d r i e d using sodium. The g a s e s were f u r t h e r d r i e d b e f o r e e n t e r i n g t h e i o n i z a t i o n chamber. Care was a l s o t a k e n t o s e e t h a t t h e d e n s i t y o f water vapour i n s i d e t h e chamber was always maintained much below i t s s a t u r a t e d vapour d e n s i t y a t room temperature t o avoid p o s s i b i l i t i e s o f e r r o r i n p r e s s u r e measurement.

Ammonia h a s n o t been i n v e s t i g a t e d f o r over a long R e s u l t s i n Water Vapour. C u r r e n t growth ( l o g I-d) time. I n view of t h e r e c e n t i n t e r e s t i n it ( 7 , 8 ) , p l o t s became i n c r e a s i n g l y l i n e a r f o r E / N > 152 Td P a r r and Moruzzi ( 5 ) i n v e s t i g a t e d attachment i n d i c a t i n g t h a t

n / ~

becomes n e g l i g i b l e over thLs p r o c e s s e s . o n l y o t h e r s t u d i e s made i n t h i s g a s were region. a / ~ and ~ I / N o b t a i n e d from t h e s e measurements of B a i l e y and Duncanson ( 9 ) and Bradbury ( 1 0 ) . P a r r a r e shown i n f i g u r e s 1 (rl/N) and 2 (a/N). Fig. 1 and Moruzzi's n / N a r e 20% h i g h e r t h a n t h o s e of shwos t h a t t h e p r e s e n t d a t a o f n / N a r e i n good Bailey and Duncanson, while t h o s e of Bradbury a r e agreement only with t h o s e of Crompton e t a 1 ( 3 ) and t e n t i m e s lower; while t h e s e Q i s c r e p a n c i e s e x i s t i n d i f f e r from t h e d a t a o f o t h e r s ( 1 , 2 , 4 , 5 ) . a/N shown q/N, t h e r e appears t o be no d a t a on t h e measure- i n f i g . 2 a g r e e with t h e d a t a o f Prasad and Craggs

ments of a/N. (2) and Ryzko (4) only t o w i t h i n

2

3% over t h e

1n view of t h e s e , measurements were made i n b o t h e n t i r e range o f E/N s t u d i e d . q/N were found t o be t h e s e g a s e s and a/N and n / N were a c c u r a t e l y independent o f g a s p r e s s u r e s suggesting t h a t e v a l u a t e d over t h e range E/N = 70 t o 150 Td ( f o r attachment a r i s e s i n t h i s g a s through d i s s o c i a t i v e q/N) and 70 t o 2400 Td

(i)

over t h e p r e s s u r e range

. -

attachment p r o c e s s r e p r e s e n t e d a s e

+

HZ0 + H-+ OH.

1 b

5 t o 20 Torr (20°c) ( N = 16.5 x 10 t o 66 x l ~ ~ ~ c m - ~ ) .

R e s u l t s i n Anrmonia. C o e f f i c i e n t s and a/N measured a r e shown i n f i g . 3 and 2 r e s p e c t i v e l y . The Experimental technique: The experimental a p p a r a t u s p r e s e n t (n-a)/N v a l u e s a r e lower t h a n t h o s e of used was of a u s u a l form f o r t h e measurements of Moruzzl and P a r r ( 5 ) and Bailey ( 9 ) and a r e higher prebreakdown c u r r e n t s by tine Townsend method u s i n g t h a n t h o s e of Bradbury (10) ( f i g u r e 3 ) . F i g . 2 shows high vacuum t e c h n i q u e s . D e t a i l s were g i v e n by Mailer only t h e p r e s e n t d a t a on a/N a s no o t h e r d a t a and Naidu ( 1 1 ) . Before t h e ~0mmencement of measure- appears t o be a v a i l a b l e f o r comparison. A s was

ments, t h e i o n i z a t i o n chamber was evacuated t o observed i n water vapour, no p r e s s u r e dependence of

.

3y T o r r , t h e pumps were i s o l a t e d and g a s was leaked

n / ~

was observed i n t h i s g a s a l s o i n d i c a t i n g t h a t i n ( s e e below). The g a s p r e s s u r e s were measured t o attachment a r i s e s mainly through d i s s o c i a t i v e

+

1 % u s i n g a s i l i c o n e o i l manometer (D.C.705). The

-

p r o c e s s e s .

i o n i z a t i o n c u r r e n t s were r e a d t o

2

1 % ( K e i t h l e y

References E l e c t r o m e t e r , t y p e 640) and t h e a p p l i e d v o l t a g e s

were measured t o

+

0.5% (DM 752, E l e c t r o n i c s 1. K u f f e l , E . , Proc. Phys. Soc.,

74

(1959) 297 Corporation of I n d i a ) . Under t h e s e c o n d i t i o n s , t h e 2 . Prasad. A . N . and Craggs, J . D . , Proc. Phys. Soc., e s t i m a t e d e r r o r s i n and n / N were about

t

2%.

-

76 (1960) 223

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979738

(3)

3. Crompton, R.W., Rees, J.A. and Jory, R.L., Aust, J. Phys.,

18

(1965) 541

4. Ryzko, A., Arkiv. Fys.,

32

(1966) 1 5. Parr, J.E. and Moruzzi, J.L., J.Phys. D:

Appl. Phys., L(1972) 514

6. Moruzzi, J.L. and Phelps, A.V., J. Chem. Phys., 45 (1966) 4618

-

7. Melton, C.E., J. Chem. Phys.,

45

(1966) 4414 8. Searles, S.K. and Kebarle, P., J. Phys. Chem.

72 (1968) 742

-

9. Bailey, V.A. and Duncanson, W.E., Phil. Mag., 2 (1930) 145

-

10. Bradbury, N.E., J. Chem. Phys.,

2

(1934) 827 11. Maller, V.N. and Naidu, M.S., J. Phys. D:

Appl. Phys., z ( 1 9 7 4 ) 1406

Fig. I . Attachment coefficignt (II/N) in water vapour.

-

present values,A Parr et a1

(51, A Ryzko ( 4 ) , Crompton et a1 ( 3 ) , o Prasad et a1 ( 2 ) and

+

Kuffel ( 1 ) .

Fig. 2. Values a / ~ as a function of E/N in water vapour and ammonia.

A

present data in water vapour, B present data in ammonia, A Ryzko ( 4 ) an5

.

Prasad et a1 (2) both in water vapour.

Fig. 3. Values of (n-a) /N as a function of E/N in ammonia.

-

Present data, Parr et a1 ( 5 ) o Bradbury (10) and

+

Bailey et a1 ( 9 )

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