Chemiluminescent reaction processes in vacuum system operating in micron pressure regio

Applebaum, D.

Harteck, P.

Reeves, R. R.

English

NASA Technical Reports Server

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I 1 
c 
c 
Chemiluminescent React ion Processes P e r t i n e n t  t o  
the  Chemosphere i n  the M i c r o n  Pressure Region 
by 
P o  Harteck,  R.R. Reeves and D o  Applebaum 
Chemistry Department, Mason Labora tory  
Rensselaer Po ly techn ic  I n s t i t u t e  
Troy, New York 
January 1965 
ABSTRACT got;-Qo 
Some atom r e a c t i o n s  which r e s u l t  i n  l f g h t  emfss ion have 
been s t u d i e d  fn  a vacuum system o p e r a t f n g  f n  the 5 t o  30 m i c r o n  
pressure reg ion .  
cesses may dominate i n  c e r t a f n  cases as was shown p r e v i o u s l y  f o r  
t h e  n l t r i c  oxide-oxygen atom r e a c t f o n  and the  s u l f u r  monoxfde- 
A t  these low pressures two body r e a c t i o n  pro-  
oxygen atom r e a c t f o n .  
The v f s j b l e  chemflumfnescent recombfnatfon r e a c t f o n  of 
n i t r o g e n  atoms a t  low pressures approaches second order  whf  c h  can 
be a t t r i b u t e d  t o  an i n v e r s e  p r e d f s s o c i a t f o n  process. A t e n t a t i v e  
mechanism can be g iven as: 
N + N e N ,  5E+#N2 B 3 n + N 2 A  3Xu + + hv, 
9 9 
where t h e  r a t e  f o r  the  l f g h t  emfssfon i s  es t fmated as k =: 10''9*' 
I 
I (cm3/par t i  c t  es] sec-1 
https://ntrs.nasa.gov/search.jsp?R=19650020939 2020-03-17T01:52:49+00:00Z
, z  
.' 
L 
, 
2. 
I n t r o d u c t i o n  
I n  general  chemiluminescent r e a c t i o n s  i n  the upper 
atmosphere can be d i v i d e d  i n t o  two groups) those o c c u r r i n g  
between ambient r e a c t a n t s  and those due t o  a d d i t i o n  o f  a r e a c t -  
an t  i n t o  the  atmosphere by r e l e a s e  from a rocket .  
number o f  d i f f e r e n t  r e a c t i o n s  a r e  t h e r e f o r e  o f  i n t e r e s t ,  but 
i n  almost a l l  atoms a r e  invo lved.  
A l a r g e  
Four types o f  r e a c t i o n s  which may occur t o  produce 
1 i g h t  emiss ion p e r t i n e n t  t o  the  upper atmosphere are:  
F i r s t ,  a general  exothermic two body r e a c t i o n  such 
as 
( 1  1 t 0, + H + 0, + OH 
where the 0H'emi t s  the  we1 1 known Meinel  bands. 1 
A second type i s  due t o  the d i r e c t  t h r e e  body r e -  
combinat ion as f r e q u e n t l y  occurs i n  atom recombinat ion such 
as t h e  emiss ion of  NO b e t a  bands i n  the  N p l u s  0 atom recom- 
b i n a t  i o n  . 2 
A t h i r d ,  i s  a d i r e c t  two body recombina t ion  as w i t h  
3 Y4 N O  and oxygen atoms w i t h  t h e  emiss ion o f  a continuum: 
NO + 0 + NO, + hu 
A f o u r t h  p o s s i b i l i t y  i s  the  s i m i l a r  two body recom- 
b i n a t i o n  by an i n v e r s e  p r e d i s s o c i a t i o n  process. 
3 The r e a c t i o n s  o f  n i t r i c  o x l d e  w i t h  oxygen atoms, 
and s u l f u r  monoxide w i t h  oxygen atoms5 havebeen p r e v i o u s l y  
s t u d i e d  i n  our low pressure r e a c t i o n  vessel .  The purpose of 
3. 
t h e  present  work was t o  extend t h i s  work t o  s tudy  the  a f t e r -  
atoms. 
Ex per i men t a 1 
The 
glow and recombina t ion  process of n i  t rogen 
ow pressure sys tem prev ious  y r e p o r t e d  has now 
been used f o r  the  s tudy o f  the  chemiluminescent emfssion due 
t o  n i t r o g e n  atoms, ;.e. the  Lewis Ray le igh  a f te rg low;  see 
F i g u r e  1. For t h i s  purpose severa l  minor m o d i f i c a t i o n s  were 
necessary. I n  t h i s  case a condensed D.C. d ischarge was used 
t o  produce re1  a t i v e l y  h i g h  concent ra t ions  o f  n i t r o g e n  atoms 
( 3  t o  5%). 
gauge ( D i f f e r e n t i a l  pressure meter, Model 306-Decker Corp.) 
where the  response i s  independent o f  the  n a t u r e  of  the  gas. 
The a l p h a t r o n  gauges p r e v i o u s l y  used were n o t  s t a b l e  when a 
coiideiised d ischarge was r u m i n g ,  whereas the  DPM was unaf fec-  
t e d  3y e l e c t r i c a l  no ise.  
The pressure was measured by use o f  a diaphram 
Resu l ts  
The r e l a t i v e  l i g h t  i n t e n s i t y  of t h e  Lewis-Rayle igh 
a f t e r g l o w  was measured versus pressure i n  analogous f a s h i o n  
t o  t h e  prev ious work, 3 9 5  This a f t e r g l o w  i n t e n s i t y  increased 
w i t h  p ressure  by p2=5O*O*'0 i n  the  pressure range o f  5 t o  30 
microns. See Tab le  I. The s lope o r  exponent i s  e q u i v a l e n t  t o  
t h e  e f f e c t i v e  o r d e r  of the r e a c t i o n  and was g e n e r a l l y  h igher  
when measured i n  a h igher  pressure r e g i o n  - 10 t o  27 microns. 
The a d d i t i o n  o f  he l ium o r  argon was made t o  vary 
t h e  e f f e c t  o f  t h e  t h i r d  body as i s  w e l l  known f o r  t h e  Lewis- 
4. 
Ray le igh  a f te rg low,  and i t  was no ted  t h a t  the a f t e r g l o w  I n t e n -  
s i t y  was now very  c l o s e  t o  second order  i n  t h e  whole 8 t o  27 
micron r e g i o n -  See Table I. 
s i t y  was measured when the  gas was expanded f rom 200 t o  lop 
and the  analogous r e s u l t s  had been obtained. 
I n  a d d i t i o n  the change o f  fntcn- 
I t  should be noted t h a t  the  observed emiss ion I n  the  
v i s i b l e  r e g i o n  i s  i n d i c a t i v e  o f  o n l y  a p a r t  o f  the o v e r a l l  r e -  
combinat ion and i s  t h e r e f o r e  no d i r e c t  measure o f  t h e  t o t a l  
r a t e  and o v e r a l l  o rder  f o r  the recombinat ion o f  n i t r o g e n  atoms. 
No e f f e c t  o f  l i g h t  emiss ion due t o  w a l l  c a t a l y s i s  
6 was a n t i c i p a t e d  or observed as was r e p o r t e d  w i t h  oxygen atoms, 
Discuss ions 
Desp i te  many s t u d i e s  i n  t h e  f i e l d  o f  a c t i v e  n i t r o g e n  
t h e r e  a r e  fundamental problems which s t i l l  e x i s t .  One ques t ion  
i n v o l v e s  the  problem o f  n i t r o g e n  atom c o n c e n t r a t i o n  versus the  
c o n c e n t r a t i o n  o f  metastable molecules and r e a c t i v e  species de- 
pending on the  method o f  generat ion of t h e  a c t i v e  n i t r o g e n  and 
t h e  means used t o  determine these concentrat ions.  
The mechanism o f  the recombina t ion  appears t o  be 
+ + 
q u i t e  complex i n v o l v i n g  an i n i t i a l  f o r m a t i o n  o f  51: 3 ~ u ,  
and/or 'C+ s t a t e s  as r e q u i r e d  by the  c o r r e l a t i o n  r u l e s  o f  
Wigner-Witmer. A general  mechanism has been g iven i n  some de- 
The chemi- t a i l  which can e x p l a i n  many o f  t h e  observat ions.  
luminescence recombina t ion  i s  apparent ly  o n l y  a f r a c t i o n  o f  t h e  
t o t a l  recombinat ion.  The measured o v e r a l l  r a t e  c o e f f i c i e n t  i s  
9, 
g 
8,9 
5. 
3 x 10m32 (cm3/pa r t i c l e ) *  sec-'; t h e  r a t e  f o r  chemiluminescent 
recombina t ion  emiss ion  may be o n l y  a f r a c t i o n  o f  t h i s ,  o r  about 
( ~ m ~ / p a r t i c l e ) ~  sec- ' .  10 
The usual  mechanism considered for  n i t r o g e n  atom r e -  
combinat ions r e s u l t s  i n  a t h i r d  o rder  dependency f o r  the l i g h t  
emiss ion  as w e l l  as f o r  N-atom consumption. 
I n  the  present work p r e c i s e  measurements were made 
o f  t he  order  o f  t h e  l i g h t  e m i t t i n g  r e a c t i o n  i n  the 5 t o  30 
mic ron  pressure reg ion .  The order  observed was d e f i n i t e l y  
l e s s  than t h r e e  (average 2.50) and w i t h  m ix tu res  c o n t a i n f n g  
more than 90% argon o r  helium, was around two. A r e a c t i o n  
o rde r  between 2 and 3 cou ld  be i n t e r p r e t e d  t o  mean t h a t  com- 
p e t i n g  second and t h i r d  order processes a re  occu r r i ng .  Argon 
o r  he l i um a re  l e s s  e f f i c i e n t  as t h i r d  bodies and would r e s u l t  
i n  reduc ing  the  t h i r d  o rder  c o n t r i b u t i o n .  
argon and he1 ium, the re fo re ,  l end  suppor t  t o  the  i n t e r p r e t a -  
t i o n  o f  competing second and t h i r d  o rde r  reac t i ons ,  where t h e  
second order  r e a c t i o n  can now dominate. 
The r e s u l t s  w i t h  
Several processes may be considered t o  account f o r  a 
second o rde r  dependence o f  the l i g h t  emission. 
a t  low pressures appeared as a continuum, a d i r e c t -  recombina t ion  
o f  atoms would appear l i k e l y .  A l t e r n a t e l y  i f  the s p e c t r a l  char-  
a c t e r  o f  t he  emiss ion  does not change d r a s t i c a l l y ,  i t  would 
seem most p robab le  t h a t  an inverse p r e d i s s o c i a t i o n  mechanism i s  
I f  the emiss ion  
occu r r i ng .  
weak , 
a r e  d 
b y  us 
~ ~~ 
6. 
The l i g h t  emiss ion i n  t h e  m i c r o n  pressure i s  very  
and t h e r e f o r e  h i g h  r e s o l u t i o n  spec t roscop ic  measurements 
f f i c u l t  t o  o b t a i n .  Low r e s o l u t i o n  s p e c t r a  were ob ta ined 
ng a l a r g e  s l i t ,  w i t h  a t ransmiss ion  g r a t i n g  a t tached t o  
a 3 5  mrn camera. From these s p e c t r a  i t  appeared as i f  t h e  type 
o f  emiss ion a t  low pressures, about lop, was approx imate ly  t h e  
same as a t  h i g h  pressure, 300p; a d i s t i n c t i o n  between bands w i t h  
sharp  l i n e s  and d i f f u s e  band emiss ion o b v i o u s l y  was impossib le .  
By u s i n g  t ransmiss ion  f i l t e r s  i n  f r o n t  o f  t h e  p h o t o m u l t i p l i e r ,  
i t  was p o s s i b l e  t o  measure r e l a t i v e  i n t e n s i t i e s  over  var ious  
p o r t i o n s  of t h e  spectrum o f  the  a f te rg low.  The r a t i o  o f  in-  
t e n s i  t i e s  changed between experiments a t  h igher  and lower pres-  
sures,  and t h i s  may be i n d i c a t i v e  i n  t h i s  case o f  some changes 
i n  t h e  charac ter  o f  t h e  a f te rg low emisslon. 
i n  t h i s  manner a r e  s u b s t a n t i a l .  See Table I1 
Changes observed 
Since a second order  dependency i s  o b t a i n e d  f o r  the  
l i g h t  e!nission and t h e  e n i s s i o n  i s  n o t  a continuum, i t  may be 
reasonable t o  conclude t h a t  some fnverse  p r e d i s s o c i a t i o n  process 
i s  opera t ive ,  such as: 
+ 4- 
N + N-N, 5 Z  e N ,  B3n9 + N,A3ZU + hv ( i n v e r s e  p r e d i s -  
9 
s o c i a t i o n )  
compared t o  t h e  g e n e r a l l y  accepted t h r e e  body process: 
+ 
N + N + M#N, 5Z+----IY)N2 B3n -* N2A3Zu + hv ( t h r e e  body 
g 9 
combinat ion).  
Under these c o n d i t i o n s  the  emiss lon spectrum should 
be d i f f u s e  hav ing  a maxima i n  those r e g i o n s  where t h e  band 
7. 
heads had been observed. 
i n t e n s i t i e s  w i l l  not be the same as  when t h e  N, 5~ 
N, B3g were s t a b i l i z e d  by c o l l i s i o n s .  
I t  is l i k e l y  t ha t  t h e  r a t i o  o f  these 
+ 
and/or 
!3 
9 
T h e  r a t e  of the two body inverse pred issoc ia t ion  pro- 
cess  was estimated as (cm3/particle) sec". T h i s  i s  100 t o  
1000 times slower than t h e  r a t e  of the  reac t ion  N O  .f 0 -+ NO, + hv. 
In connection with t h e  upper  atmosphere, however, t h e  
net  consumption of N-atoms would s t i l l  be due  to  reac t ions  over 
molecular oxygen. The r a t e  fo r  t h i s  reac t ion  ( N  + 0, -+ N O  + 0 )  
i s  about (cm3/particle) set" w i t h  6 k i l o c a l o r i e s  heat o f  
ac t iva t ion  with increasing temperatures above 100 kilometers 
a l t i t u d e  t h e  r a t e  would increase and N-atoms w i l l  r eac t  much 
more r ead i ly  with the molecular oxygen, than i n  a two body re-  
combination process w i t h  another N-atom. 
Ackrlowl edqernent 
T h i s  work was supported by Air Force Cambridge Research 
Laborator ies  under cont rac t  number AF 19(628)-4068, and t h e  
National Aeronautics and Space Adminfstration u n d e r  grant NGR- 
33 -0 1 8-0 1 6 
References 
1. 0. Garv in ,  H.P. B r o i d a  and H.J. Kostkowski, J. Chem. Phys. 
32 880 (1960) 
2. R. A. Young and R. L. Sharpless, J. Chem. Phys. 39, 1071 
(1963) 
3. R. R. Reeves, P. Harteck, and W. H. Chace, J. Chem. Phys. 
- 41 , 764 (1964) 
4. P. G. Doherty and N. Johnathan, Discuss ions of the Faraday 
S o c i e t y  2, 73 (1964) 
5.  T.R. Rol fes,  R.  R. Reeves, and P. Harteck,  J. Phys. Chem. 
( i n  press)  
6. P. Har teck and R.  Reeves, Discuss ions o f  the  Faraday 
S o c i e t y  37, 82 (1964) 
G. Herzberg I' Molecu la r  Spectra and Molecu la r  S t r u c t u r e  
Spect ra  of Diatomic Molecules"  D. VanNostrand Co. I n c .  
7 .  
(!?SO) 
8. A. G. Gaydon I '  D i s s o c i a t i o n  Energies and Spectra o f  
Diatomic Molecules", Dover Pub1 i c a t i o n s ,  I n c .  (1950) 
9. J .  Berkowi tz ,  W. A.  Chupka, and G. B. K is t iakowsky,  J .  Chem. 
Phys. 25, 457 (1957)s K. P. Bayes and G. B. Kostiakowsky, 
J. Chem. Phys. 29, 949 (1958), J. Chem. Phys. 32, 992 (1960) 
10. J. F. Noxon, J. Chem. Phys. 36, 926 (1962) 
TABLE I 
E q u i v a l e n t  order o f  r e a c t i o n ,  n, as measured by 
r e l a t i v e  emission I n t e n s i t y  w l  th  i n c r e a s i n g  
pressure ( 1 - p  ) n 
Pressure r e g i o n  
100% N, 
5 t o  12+ 
9 t o  1811 
10 t o  2 7 1  
5% N, ba lance A r g m  
12 t o  18p 
10% N, balance He1 {urn 
9 t o  1 8 ~  
8 t o  27p 
12 t o  2 7 1  
Observed r e a c t f o n  order,  n 
2.49  
2 . 5 6  Average = 2.50 $ 0.10 
2.60 
1.90 Average = 1.90 ? 0.10 
2.1 5 
1.93 Average o 2 . 0 5  0.10 
2.07 
Atom concent ra t ions  were mainta ined r e l a t i v e l y  constant  between 
3 and 5% 
* .  .- , e  - , '  I . 
TABLE I 1  
Observation of R e l a t i v e  I n t e n s f t i e s  o f  
the  Ni t rogen Af terg low 
Corning F i l t e r  3-68 3-66 2-61 
For 100% N, 1.0 0.53, 0.308 2 0 0 ~  Pressure 
1 .o 0.44, 0.25, lo+  Pressure 
For 5% N, 1 .o 0.52, 0.30, 200p Pressure 
Bal ance Argon 1 .o 0.41, 0.25, lop Pressure 
Corning FA1 ter 3-68 Transmits the  r e d  ye l low and green 
3-66 
2-51 Transmits the r e d  
Transmits the  r e d  and yel low 
Measuren(?:its were made on ly  i n  the v i s i b l e  regfon o f  the  spectrum 
Y 
r 
U cn 


Chemiluminescent reaction processes pertinent to the chemosphere in the micron pressure region

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