Product Channels of the N2 (A3Σ+u) + O2 interaction

CllLhllCAL

mcnml problem of excilation-transfer and rcactiwty in n simple system. bur also hnvc inlportnnt spphmtlons

1. Introduction Al~l~o~gh

16 April 1982

PIIYSICS LIITLRS

IIIC otcrall

rake of the title rcxtion

is now

sc~encc. Reachon

III upper atmosphere

(3) represenrs

very well known 1I-31 . 11sproducl chdnncls JrC much less well cllJrJctsrl/cd. Five SCLSof products arc cucr-

a potential

gclicJliy

can provide substantial source terms oiinfwd

N,(A)

.lllowlld + 0, --L N,(X) _ _

+ 0;

-+ N#)

+ G5.l

+ 2O(‘P)

- N,O(X)

cV.

(1) (2)

+ Ot3P) + 2 8 cV.

(3J)

+ NO(X)

-+ N0,(7Al I Icrc. (I)

IS cwlrJtion

(4)

to Jny xcssslblc

(5)

dloms.

NZO. (4) .I four-ccntcr rwction rcJrrJngcmcnr

SpccLrometrtc slowly

pumped

thcrcfore,

transfer IO form

for such mtcr-

2. Experimental

in which IWO bonds arc

The appdrdtus used prcvlously XicJIlon

transfer.

This has not been ob-

scrvcd, IICIICCboth (4) and (5) arc ncglectcd

In the cn-

suuig discussion. to (3) Jrc of mtcrcst

mcdsursmcnt

of

not only as a funda-

modified

of a twclvc-liter

UV resonance fluorescence

being filled slowly a dynamic

version of one glass bulb

to the flow tube 5 cm downstream

pressure (2 Torr) .md qudnlitJtivc

was a slightly

(see fig. I of ref. [7])_ The main mod-

was the addition

vacuum

570

both O-atom and

bccJuse the reaction occurs well downstream

N,(A)

chJnncls (I)

to mtasurc

in 3 rapidly pumped discharge-flow

to form two NO. and

for cllhcr (4) or (5). The rormcr should

idcn~lficJ~lon

system whcrc cumu-

system. where thcrc IS Icss opportunity

conncctcd

The

dischJrge-ailcrglow

and mass pulsed, very

side reactions arc not ruled out. We have.

undcrtakcn

kdd IO subscqucnt NO y-band emission JS J result of + NO clcrtation

analysis of a repetiltvcly

or the active discharge.

brohcn Jnd Iwo others iormcd. Thcrc IS no c\pcrlmcn1~1cvidcncc

_Zrpfs [ I1 erprrr-

and (3), (4). and (5) arc

reJctlvc chJnncls, (3) being 0-Jtom (5) an unhhcly

so far, to the quesrion of

mental work was based on spectroscopic

krcncc.

slate

of O1_below the ksociation hmlt. (2) IS dlssocidtnx chcihlwn IrJdCr leading 10 the production of two groUUd-SiJfC oxygen

contribution,

product channel idenlity apart From qualitatrvc obser-

NZO-productlon

+ 0.95 cV.

radiation

and of NO, [4.5]. ZipTs [I ] finding oi60 2 20% N,O fonnJtlon per N,(A) rcactlon has been the only drrect

lativc unpurity

+ -1.3 cV.

lransfcr

whose infrared and reaction unh O(l D)

photolysis,

v;IIrons of O-atom ~ormarron [6]

(3b)

) + N[‘S)

chcmdummcsccncc,

chpcrimcntal

+ I I cV,

-N,O(X)+O(‘D)+0_79cV. 4 NO(S)

l~~gl~lt~ludc source of N20

(~20

min)

detectlon

to within

from the cell. After

7-s of flow tube

in the course of an cxperunenr

cahbration,

or of

this bulb was Isolated and con-

nected IO an evacuated, 107 cm long, 0.4 cm i.d. col0 009-2614/82/0000-0000/S

02.75 0 1982 Nordl-Holland

CHEMICAL

Volume 87. number 6 lection

16 Aprd 1982

PHYSICS LI3lTCRS

tube of either 304 stainless steel or quartz of

~15 cm3 volume. One end of this tube w3s then mlmersed in liquid hehum IO cryopump sample. Following

pumpdown

the entlre gas

to 5 0.02 Torr, the col-

lcction tube was isolated from the bulb, heated to =150°C. snd the gas sample, now at ~3 atm pressure, was analyzed for N20 using electron capture gas chromatography (Pcrkin-Elmer. model Sigma-3, N2 carrier g3s, 4 ft. carbosieveS column 31 15O”C, with 5 cm3 sample valve). For each gas sample. up to 12 SUCCCSSIV~

chromatograms were run in order to guard agamst mcomplctc mlxmg III the long Iubc. The 3ccuracy and sensitivily

of the CC an3lysis of N,O 3rc estimated

be +I0% and 4 ppb. respectively. responds IO 3 dctectlon flow

This sensiiivlty

IO

cor-

cme3 in the

limit of 3, X IO*

tube.

Laser-induced

tluoresccnce

(LIF) detection

Tlg I. Gas chromatogrdphlc ahbratlon and nw~surcmcnt OI’ lNzOl -. SKIIIC uhbration< rcprcrcnt IWO IO iibc dn.dyrcs. each consittmg

of

bration

of three IO six chromarograms.

c\pcrimcnls

whcrc cxh

pomt

X. d)name

rcprc~encs

l-l-

ah-

I6 con-

N?(A) was csrricd out 3s before 121. The 0(3P) conccn~ratton ~3s measured by resonsnce lluorcsccncc [Z] . cahbraled absolutely using .srn~II, mcasurcd addI-

and the si\ CC mcsswcmcnts oi N-0 product irom N:(A) + Oz. mhcre each anal>~~s rcprescn,s IO- 12 CO”SCCUII~C ‘hroma-

tlons of NO to excess N-atoms produced

togrlms

m

3

micro-

chromJtogr.mls The inw

sccutlrc

c&brJrton

~IOWS tlic

lmc

wave

discharge in flowmg N,/Ar mutures. Another mlcrowave dischsrge in l-lo&g He 31 I.5 Torr contammg

3

tract of 02 served as the VW

lamp. The monochromator and the photomulttpher

sgnal

IO s mlervals. The detection (5-10)X

lo8 cm_3 (S/K=

The N,O collection

w3s

31

pulse counted

cahbratlon

pomts 3grcc IO wlthm ==:+l0%.

I mm,

Dynanuc

for

JISOrun and g3vc no N20 slgnal as ehpecIcd.

Linus W.IS In the range

blank cahbr3tlons

Total pressure (==3-Torr),

ulthout

added N,O were

flow velocity

(1~= 40 nl

S-I except lower in N + NO fitr31Ions for 0-3Iom

I)_

and detectlon

sysrem was care-

fully chcckcd using both sta11c and dynamic lions. In the former,

3nd dynamic

reson3ncc

s.111 widths were seI

five separate cahbratIon

cahbra-

brarlon).

and gas purificatton were

JS

cah-

dcscrtbed e.trlicr

1’1.

mixtures

were prepared in the 0 to 500 part per billon (ppb) range and analyzed repeatedly

under various condl-

tlons of inlet sysrem temperature. shown in fig. I. hlore importantly, tions were performed

dynamic

dtscharge was off and th3t known

N20 greatly diluted

lures. The final 93s composirion 3nd 100-300

small flows of

closely duphcarcd

ppb NzO corresponding

calibrations

+ 0,

were carried out using the

points in

loss, since static

of

and of

tunes IO

31 various

ssmples

ConccntrdtIon

Its removal

of Ihe s~rnul-

corwstcd

twelve-ltter

resonance fluorescence.

out

stainless steel and one using the quartz collection tube to make sure that there w3s no loss of N20 m the colfig. 1, it is clear that there was no N,O

VW

Ihat

to a 7_0-

collection

ys~s and of 0-dtom N?(A)

reactlon. Two

lection procedure. From the corresponding

taneous

mi..-

i.e. 80% Ar. 20% N2, 0.6%

60% yield of N20 in the N?(A) such dynamic

except Ihat Ihe

with O2 were added to Ar/N2

of Ihe resction mixtures. 0,.

The prmcrpzd ckpcrtments

c3hbra-

whtch were the exact equivalent

of N?(A) + O2 reactlon cxpenments. Ar*

3. Results and discussions

These pomls 3re for N20 an3l-

medsurcment

by

LIF measurements

by added 0, ascertain

tltdl

wrrc

of

31~0 csrrlcd

N#.

u = 0, I .‘_)

LIF signals wcrc comparable

IO those observed before

I’_]. The absolute Ar(3P2,0)

concentration

sured indlrecrly

w3s mc3-

by reaction wiIh cxccss O-, in Ihc 3b-

scnce of added N2 under orl~crw~sc closel;mstched experimental

conditions.

In six expermicnIs,

WBSfound to bc (3.3 * 0.5) X lOI assumed that O2 dissociation Iion togcthcr

and dlssocl3Ilvc

produce 3 qu3nIitatIvc

[Ar(3P2,0)]

mte3 where II IS ckcits-

yield of 0-3Ioms 571

VO~UIIIC

S7. nunltrr

drtcctcd

6

CIICXKAL

downslreant

3s O(‘P)

1112O(31’) lVlcld from Ar’ t.mv2Iy

w11h rh.~r obr.nncd

ttc31 Ar‘

gcncr.ttion.

upstrc3m

01‘ rhc 0,

_In 17 experiments,

[7]

+ 07 ~3s compared

but wnh e~c2ss N, mi\mg

of added Rr. Th2s2 c\p2runsnrs

flou

0.66 5 0.10 for 0-atoms I c

+ Oz. 3s Jg3lllSl

for x,(A)

+ 0,

The I+ sn

ricd-our

formed

c\perimcnt.

on the assumption.

thi Ar* + Nl

in the cxpandcd thw

Beforc

reldtiv2 r3t2s mher2nt

yields xc

or channels

resulr of

me3surements

III

terms of th2

S~III rcsorxtncc dctcction

0(3Pz).

In dielr e\Pcruncnts.

prescnred

[7].

qllJllIll3ilVe.

der2rmmed

+ 0(3P).

O(‘P)

channels to be -16 : 52 : det2chon

ofO(3P)

(2)

The

compsrison

rexme

+ 0,

ncss of the Ar* rhrough gust

abovs the N?(4)

whcreJs N,

WJS

rlpxt

region must be compdred. dlfiuslon

conrrolled

mode diiruslon iirst-order Torr [IO]. ficlent

wdll

is much

radiative

WJS

retracted

inlet (se2 fig m

to

I of ref. [?I). rhr

1111smtermediate

For N?(A)

2ncrgy

and collisional cascade r3tIo oimnlall!

N,. C to B st3tes. has risen over the years

in Ar, we 3ssume which,

in lowest

diffusion [I I],

[Ia]

diatne

transition

diative

and collistonal

to1:0.75

JIl,)

[ljlandre-

IS iormed

coefbut

to N,(B

m the colh-

311_e)and then by further

processes to loser

is indeed the only initial

al cllstrlbution

[17]

3.34u=4.3nd

I%u=j

triplet

7.55 u = 0, ‘0% distribution

1. 13$%‘0=~,6%u= [I81

3ndofmuchsmJller

amounts

in higher levels. If the subsequent

of N,(A)

were controlled

by purely

(IV? first positive emission), would

r3-

~1312s

11s vibration-

product,

ofapproGm3tely

inN2(B)of4998u=0,17Gu=

b245%u=0,3l%u=

population

radlatlve

its vibratlon3l

cascade

dlstrlbutton

I, 17%u=3_,6%‘0=3,

3% u = 4, I .4% u = 5. and 0 8% u = 6. b3sed on the known tr3nsition

probabthties

conditions,

oi 3.66 D/r? = 176 s-t 31 7,

= 50 cm2 s-l

toI.

u = I, and 53 u = 2 Ie3ds to 3 vibntion3l

of the

Smce 01 WBSadded

deactivation

D,,

iransier and subsequent

(see ref. [I Z]

of the primary

stonal energy rr3nsf2r. TINS IS followed by the rapid ra-

irom the compkte-

m Ar, the corresponding smaller,

source of Nl(A)

N,(C

of the

f 0(‘S)

[9]. setrmg Do = I50 cm? s-* 3t I Torr pressure For Ar’

3

the d2t3k

+

has been

now clamt that only

ntJgmtud2

and I3minar tlow, gives 3n cff2ctive

r3te constant

m the Ar*

thrs s3mc techmque

I : 0 [ 161. Sadeght and Setser [ 161

added -~3 ms tlow tune upstreJm.

loss proccsscs for Ar* and N,(A)

m our 3nalys~s

ofN?(A)

from1.6[13]

[8!

yields from Ar* +

inJ2oror wh~h or Ar-

Although

tor 3 reL2nt review).

IiN,

transfer.

lieId

cently IO essentially

3ssumes the equkdence

to N?(A)

rhe movable

much less so.

snd Golde

pr2ssnce or dbscnc2 oi

species concentr3llon

Nz rextton.

due to

and the many

3nd O(‘P)

of 0-Jtom

ofN,O

tube must be less

populated

sc3veng2r spcc~cs SULII 3s H,O. 02 and N,(A)

the wall of tl~r tlow

are stdl in some question. The reported

2 by rcson.mcc IluorcsLence

111rhs

nex

con-

the rclatlvc

+ O(‘D).

m the msin flow. Any undcrestim3tc umphng

IO b2

oi the rc3ctlon

of 275

p3rtlcularly since both at the 0, addition point and II the CC samplmg point. there are right angle bends

consld2red

st3tes. B~ktmut3

zone to rhe

coefficient

wds

b2 e\p2ctcd.

concernr3-

cm? set, these gradients will hare largely disappeared.

us2d for son12 rmtc as

JS

N,O

inrormdtlon WJS

rc3sondbly

encrgcrxs

dlssoctatlve

have recently 0(3P)

quantltJtm

would

3nd

and the

tn keeping

[Ol . In 40 cm dnt3nce

31 3 dlifuslon

pertains to the ultunaie

[71 using

3nd deteckd

gradient

and IO ms flow 1imr from the reaction NzO sJmphng point

is neglected.

of N,(A)

(-I) The most serious assumption

3s 111ours. .my O(ID,)

the dasoclJtlon 3s

sIdering 111e 3vdktble

liltle

r3didl concentrarion

than =ZIO% and probably

of both Ar(3Pz)

qu2nkd

11~s 3

by re3ctton

the large uncer-

WIIII IIS rapid surf3ce loss, the Initial

with Ar‘

Jnd hlillcr

electron

O(3P). Although

arc shown

mus1 be dlscusscd.

by Brsskcnridgs

b2 rapidly

111

lo (3). scvcral xsumptions

in our interpretation

formed would

+

thar

N?(A)

btter

ior 3

than the N,(A)

lkter

to a 7% greatsr loss of Ar*

tion wdl rellecr that gradient

from N,(A)

(I) The dlSsOClJliOn of O1 by nxctlon ~3s rcportcd

(3) If N20 IS formed

3n3lysls. ~35 c3r-

uocxpcctcd

mrcrpret2d (I)

loss rare. This corresponds

ratio of

ilg I

scJle tns2I of

is 34 s-l

13m1125m th2sc loss 1312s. rhis difference

ul~~m~tcly produces

Tl~c [N’,O]

qu3ntltJ~n~c yi2ld

which

J

fur1hcr discussed below.

rcxtion

gas-phase quenching respectively,

ovrr the 2 ms flow tune. Considering

N,. 1.e for Ar*

y~cld of N,O

and three-body

3n cqu31

with N, mlerpositlon,

viz N,O

only (Z! z 0 5)5: iractiondl 0,

Interposed

gdve

without

lhc

times .md g3vc

rorsl of ‘10 s-l,

of iden-

inlet. repkmg

there 3re two-hod)

processes that add 96 alld 57 s-l.

quanti-

under condltlons

16 April 1982

PtIYSICS LLTTCRS

radiative

although

[ 181. Under our experimental the C + B transition

is entirely

(TV =Z 37 ns), the B + A transition

ts not.

Sadeghi and Setser [ 191 and Rotem et al. [‘_O] haw shown that the N, sionally

B, W()A,),

coupled ind

and A st3tes 3re COIII-

th3t the B * Wcoupling

rate con-

Volume 87. number 6

stants are nearly gas kinetic for N2 as a collision whose radtative

responding

lifetime.

collistonal

TV,

partner

and 0.015

? 0.006,

is ~6 ps, the cor-

somewhat

different.

interconv2rsion

times range from i e. the

N?(B) drstrtbution

to lower u.

relaxed

The rapid B * \V tnterconversion matclt

form,

tune scale of our experiments. Ar*

and the close energy say b!#‘).

on the

In the =? ms between

+ N7 mtxing and rcactton of Nr + 01,

relaxuion

oiN?(A.

u = I-3)

The further IS probably

~~msforu=3~nd~lOOmsforu=2 is reported why u>

in

slow. I e. rL,

the u = 0 and I levels are highly

may explain

populated

does not rule out the posstbiltty of the mttial NZ(C) populatton not fully

characterized

the known

kmetic

state require

metastablc

ttons of ==lOt”

reported

N(qS).

In the Ar* +

_

[??I

bctw2cn

su88csts that other reacttons

for a vcr-

N?O + 0 [33]

observed

prorlucts

yields, mcludtng,

, since N-okidcs

m tlt2 mass spcctrd of tltose

expcrtmcttts.

In VISW of 1112magnttudc

ancy. further

verification

method

[I 1 r2sults

our and Z~pl’s among dacharge

for his Lug2 N,O

psrhaps N + NO? -

of this dtscrep-

by an mdepcndcnt

expert-

is destrable.

Acknowledgement The authors

express thctr gratttudc for IIt2 temporary

to the Pcrkin-

loan 0i d gas chronia-

tograph. model Srgms 3. and assocratcd electron detector formed

and gas samphng eqtttptncnt. Laboratory

capture

311of wlticlt

very well. Thus work w3s supported

Force Ccophystcs Agency

in terms of reaction conversion

of Ar*

(B) assuming. 80% conversion

3) plus 20% dlssocktion For case (A),

and Dcfcnse

pcr-

by the Atr Nuclear

under Task S99 QAXIiD.

channels (I),

to N?(A.

of N-,(A)

respectnely.

Specific

for Nl(A,

than that for u = 0.3.9 [I

yteld. to gave

65 f 0.10,

rate constants

since the overall

u = I) is constderably X 10-tz

larger

versus L?5 X 10-t*

] , and nothing IS known regarding the u-

dependence

of product

$0131 of3

* 1 x IO-t?,

channels.

X IO-“,

Using a weighted

kt av z

I X IO-“,

and k3_av = 6 X iO-*”

cm3 s-t.

iizJv

-I-

For case B, neglecttng

the slow reaction

References

u = 0,

u = 0. I,

reacting

+ 0 are 0 33 + O.lO,O

can be asstgned only approxtmately, rat2 constant

(A) as-

to N,(A,

of N,, i.e 33% N(3S)

the fracttons

+ 0, and N20

and 0.01 ? 0.005,

a&age

smaller th;ln for

IS cxotbermiz

our results of relstivc O-atom and N20

sumtng quantitstivs

c-n-13s-l

ex-

of 530%

(2). and (3) under two sets of assumptrons

Oy,O

condt-

questton IS under investtgxlon

yteldj are interpreted

1.1):

with

but there IS tndtrect

and elsewhere

is only sltghtly

conccntra-

[‘1’1] for the formation

Thts mteresting

in our laboratory Finally,

N?(A)

of N-atom production

evidence

ncxfor whtch lhc

from A. u’ = I to S. u” = 3.

Elmer Compmy

Nz process IS as yet unresolved, psrtmental

factor

transttion

is IS

of the B

in agreement

cmB3 under sundar ehpcrtmental

tions The posstbtltty

r&as2

states. tlowevcr,

properties

a large yield of N,(A), which

Frsnck-Condon

mental

m,ty end up in as yet

and radiative

earlier studtes [?I].

llus

that a small fractton

encr8y

since Oz-dissocistton

for the (4.0)

w2rc prominently

while

? 3re present in much smaller concentrations.

of N,,

02. Thts restrictton

ly rhemloneutral

were responsible

[21],andtt

to occur m &J = ?_steps, whtch

weak. however.

The discrepancy

vtbrational

transitton

from A. u’ = 0. would

yield X. u” = 5 or 6 wtth insufficient (4 8 to 4.5 eV) to dtssociatc

ttcal transition

I f 0.13,

c3se, the large O-atom

transnton

u” = 5, and smce dtssoclatton

mtcrcon-

version plus B + A radiation should lead to N?(A) low u-levels tn very large yt2ld

In tither

yield seems to requtre J non-vertical

relattvely

of the B nnd W states for low IJ rules out any

storage of Nz in a ntetastabls

are 0. I6 * 0.13.0.8

and the k-values are correspondmgly

A -P X, smce a vertical

~0 4 ps at u = 2 to aO.1 ps at u = 5 [20]. will be further

with 02, the fracttons

(B. u =

and quote t-ast even for Ar collisions. For N, 2-5)

16 April 1982

CHCMICAL PIIYSICS LLITERS

of N(4S)

I I I E C. Zrpi. Nature 287 (I 980) 523. 111 M P lrrnnuur and t Kx~tm.m. J Ph)s Chcm 85 r19BI) 2163 13 ] L C Prpcr. C E Czkdanu and J P Kcnnxdy. J. Chcm Phys 74 (1981) 2888 141 EC. Ztpt- and S S. Prawd. Na~urc ‘87 (1980) 525 151 SS Prxrdxrd tIC.Zipf.Naturc291 11981)561. 161 J.A. Meyer. D.11. Klortcrbocr And D.W. Se~w. J Chum Phys 55 (1971) 1081 17 I W ii. Brcckcnrrdgcrmd T A btrlkr. Chcm Phys Lcltcrs 12 (1971) 437. [Sl J. Bkrmurs .md Bt t- Golde. J. Phls. Chem , submtttcd for pubhnuon. 191 L E. rcrguson, r C. rchrcnicld Jnd A.L Schmcltckopi. Adtan At. blol Phbs 5 (1969) I 573

CHEMICAL PHYSICS LEl-J’ERS

[ 101 T.R. Marrcro and I: A. Bl.tron. J Phys Chem. Ref. Data IllI

I (1972) !. I H. Holrs and D W’.Sctscr, J. Chem. Phys 68 (1978)

4848 [ 121 IVC. Clark and D W. Sctscr. J Phys Chcm 84 (1980) 2225 1131D IV.Setscr. D H Stcdman and J A Co\on, J Chem Phys. 53 (1970) 1004 [ 141J.A Kolts. H C. Unshears and D.W. Setser. J. Chcm. Phys 67 (1977) 2931. [f 5 1 hl Touzcztu and D. Pqnott, Chew. Phys Lc~lers 53 (1978) 355 1161 N Ssdeghi and D.W Serser.Chem Ph>s Letters82 (1981)3-l

16 April 1982

1171 EA. Gislason. A.W. Klcyn and J. Los, Chem. Phys Letten 67 (1979) 152. [IS] A. Loftus and PH. Krupente, J. Phys. Chem. Ref. Data 6 (1977) 113. [ I91 N. Sadeght and D.W. Sclscr. Chem. Phys. Letters 77 (1981) 30-t. [ 20) A Rotcm. I Nadter and S Rositnwaks, Chcm. Phys Letters83 (1981) 181. 1211 J.\V Drcycr and D. Perner, J. Chcm. Phys. 58 (1973) 1195.

1221 h1.l”.Cofdc. private communtatlon. [23f hl A.A. Clyne and IS. McDermrd. J. Chem Sot Fmday i 71 (I975)2189.