‘b ’

ENERGY TRANSFER I N PLANETARY ATMOSPHEREX: OPTICAL SPECTROSCOPIC STUDES

H. P. Broida, Pr inc ipa l Invest igator University of California, Santa Barbara

Final Technical Report

December 1, i970 - May 33, 1971

National Aeronautics & Space Administration, Office of Sc ien t i f i c & Technical Information (Code US), Washington, D .C. 20546.

FORWARD

Grantee :

Contract Number :

\Scientific Monitor:

Tenure :

H. P. Broida, University of California, Santa Barbara

NASA NGR-044

D r . I. G. PooIrpoff

December 1, 1973 - May 30, 1971

ii Y

A

ABSTRACT

Several different cross sections have been measured i n the laboratory

for the production of e lectronical ly excited species t h a t a re observed i n

the atmospheres of the planets. Spectra of CO; (r 211 - ?TI) and (@C - %?TI) band systems produced by the interact ion of C02 with He(2 3 S) metastable atoms

are similar t o spectra observed i n the atmosphere of Mars. Experimental

t r ans i t i on probabi l i t i es of the CO2f (x - 8) band system produced by t h i s

energy t r ans fe r process were measured using spectra with 0.32 nm resolution.

3 Recombination of t he resul tant COS gave large concentrations of CO(a

Decay of CO (a21"f - X$) Cameron bands i n a flow tube allowed a measurement of

the l i fe t ime of the CO metastable.

IT).

Also removal of the CO(a 3l7) from a

flowing arterglow gave quenching ra tes f o r N2, NO, and C02. Spectroscopic

emission from the interact ion of 58.4 nm photons with N2, 02, CO, -NH3, and

NiO has been csmpared with She pho.ton interact ion w i t h C02. Absolute cross

sections were measured fo r the production of each vibrat ional l eve l of a l l

observed electronical ly excited s ta tes . Helium metastable atoms have been

3 used t o produce metastable CS(a

afterglow.

TI) by the interact ion of CS2 with a helium

iii

TABLE OF CONTENTS

i

Page Part I

In t roduct ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Part I1

Work a t U.C.S.B.

T. S.Wauchop . . . . . . . . . . . . . . . . . . . . . . . . . 2

K.Monahan. . . . . . . . . . . . . . . . . . . . . . . . . . . 4

J.West . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

R e f e r e n c e s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 . -

T a b l e s . . . . . . . . . . . . . . . . . . . . . . . . . * . ~ . . . o . . 8

Figurecapt ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

~ i ' i g ~ r ~ s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

December 1, 19'70 through May 30,'1971 . . . . . . . . . . . 16 Appendix A: Invited Lectures and Papers; Published Art ic les

iv

-1-

PART I

INTRODUCTION

Techniques of op t i ca l spectroscopy have been applied t o understanding

planetary atmospheres.

active af'terglows and flames have been used for t h i s purpose.

had as a main purpose the teching of techniques of op t i ca l spectroscopy as

A variety of reaction systems such a s discharges,

The program has

applied t o atmospheric studies. I n addition, graduate students and postdoctoral

fellows were able t o do research a t Ames Research Center and a.t t he Molecular

Physics Laboratories a t U.C.S.B., doing spectroscopy studies relevant t o the

upper atmospheres of Mars, Venus, Jupi ter , and Earth.

-2 -

PART I1

WORK AT U.C.S.B.

T. S. Wauchop

Flowing afterglows i n ra re gases have become a useful t o o l f o r study of

ra re gas metastable atoms and ions and of various energy t ransfer processes.

Comprehensive discussions of these afterglows are given by Ferguson;’ Bell,

Dalgarno, and Kingston;‘ and Stedman and S e t ~ e r . ~

are produced i n several ways, including microwave and direct-current

These ra re gas afterglows

4 5

discharges and electron bombardment. 637

I n the helium afterglow, several helium species, He+, He ( 23S), He( 2’s) , 2 He2( C), and He: i n addition t o ground s t a t e Be(llS), have been detected.

Metastable He(2 S) atoms are rapidly converted t o He(23S) by e l a s t i c co l l i s ions

with electrons.

by addition of an electron scavenger such as SF6.l’ There i s l i t t l e production

1

8 Ionic products can be removed by using microwave heating’ or

of metastable molecular helium, He2(2 3 S ) , i n afterglows a t pressures below LO

torr.’ It is , therefore, possible t o produce anafterglow i n which He(2 3 S ) i s

the dominant energetic species.

3 When He(2 S) i n t e rac t s with a diatomic o r tr iatomic molecule, i ts

electronic exci ta t ion energy can be t ransferred t o electronic and vibrat ional

exci ta t ion of the molecule. Using the flowing

1, we have measured the r a t e s of production of

observed spectroscopically between 199 and 750

afterglow system shown i n Fig.

e lectronical ly excited molecules

nm in the reaction of He(2 S) 3

- 2 4 . 2 Table I gives the production r a t e s for CO; A Il and B with CO,.

CO X

obtained the photon t r ans i t i on probabi l i t i es fo r the CO:

Z and

and b 3 C. Using spectra s imilar t o the one shown i n Fig. 2, we 4 - X band system

given i n Table 11.

3 13 Observation of the CO Cameron band (a TI - xlF) i n the atmosphere of Mars

3 has lead t o an increase i n in t e re s t i n possible production process of CO(a ll).

Recently several new measurements have been made of the l i fe t ime of the

metastable s t a t e . 11’12’13214

deactivation r a t e s of C O ( a

Measurements have been made of co l l i s iona l

3 12 TI) with various atmospheric gases.

3 One possible method proposed fo r the production or” CO(a ?) i n the Martian

atmosphere was the dissociat ive recombination of Cog. ’* We have produced high

concentrations of CO: by He(z3S) interact ion with CO,. Spectra taken i n t h i s

system confirmed the production of C O ( a 3 ll) (see Fig. 3).

Decays of the CO metastable i n t h e flow tube were used t o measure the

radiat ive l ifetime and quenching rates . The value of the l i fe t ime measured i n

t h i s manner was 7 - + 4 msbc. Measured quenching r a t e s and cross sections for

3 the react ions of CO(a

estimate of the recombination r a t e of CO; a lso was obtained.

be between 8.5 and 20 x

published values.

n ) with N2, NO, C02, and He a re given i n Table 111. An

It was found t o

cm3 sec-l, within an order of magnitude of

16

2 2 Quenching of CO(a %) by NO was found t o produce EJO A C and B TI; r e l a t ive

production e f f ic ienc ies f o r each vibrat ional l eve l a re given i n Table IV. 3 By estimating losses of CO(a n ) due t o diffusion and quenching, we found

t h a t i n order t o account f o r the in t ens i t i e s of the Cameron bands observed

more than 5% of the CO; present must give CO(a 3n) on recombination.

-4-

K. Monahan

Recent space probes and s a t e l l i t e s have increased in t e re s t i n the e f f ec t s

of so la r radiat ion on gases found in planetary atmospheres. Laboratory s tudies

of 58.4 nm photon interact ion on C02 l7 were carr ied out a s a r e s u l t of Mariner 18 probes to Mars. Ground-based and s a t e l l i t e studies of the ea r th ' s upper

atmosphere make it desirable t o fur ther understand the interaction 02 prominent

so la r emission features19 on gases such a s N2 and 02. The proposed "grand tour"

of the outer planets w i l l probably show spectra produced by the interact ion of

solar radiat ion on NH and CH4 i n the atmosphere of Jupiter. 3 Commercial production of t h i n aluminum f i l t e r s t ha t pass wavelengths

between 30 and 70.nm have made it possible t o p r d u c e an intense 58.4 nm light

source i n t h e laboratory.

arrmgement,l7 we have obtained r e l a t ive production cross sections for the

Using the previously described experimental

interact ion of 58.4 nm photons wi th N2, 02, CO, N20, and NH3.

with El4, C2H5, NO2, and H20 gave no emission i n t h e wavelength range between 200

Interact ion

and 750 nm.

Using the absolute cross section for production of the CO; (r - H) band

system by photoionization of C02 at 58.4 nm17 as a standard, absolute cross

sections f o r the production of each detected band system were measured,

Relative populations of each vibrat ional l eve l observed were

calculated from i n t e n s i t i e s using the relat ion, 23

+v" CY Nu' qvlV" v 3

They are given i n Table V along with absolute cross sections for the

production of each vibrat ional level .

-5 -

5. West

Production of CO(a 3 g ) from Cog suggests t h a t CS; recombination may

produce CS(a 3 TJ). Addition of CS2 t o a He(2 3 S) af'terglow produces a green flame,

Spectra of this flame show band systems i n the green region of the spectrum that

are as yet unidentified and bands of CS (a ll - x3). 21 Production of a

CS(a

3

3 3 TI) afterglow s i m i l a r t o the CO(a n) afterglow described e a r l i e r i n t h i s

report provides a good experimental s i tua t ion t.o study the properties of the

CS metastable.

REFERENCES

1.

2.

3.

4.

5;

6.

7.

8.

9.

E. E. Ferguson, Phys. Rev. 1-28, 213 (1968).

K. L. Bell , A. Dalgarno, and A. E. Kingston, J. Phys. B 1, 18 (1968).

D. W. Setser and D. Stedman, Progr. React. Kinetics 6, 193 (1971).

A. I. Schmeltekopf and H. P. Broida, J. Chem. Phys. - 39, 1261 (1963).

J. L. Dunn, Ph.D. thes i s , Department of Chemistry, University of

California a t Santa Barbara, 1966.

E. E. Ferguson, R. C. Fehsenfeld, and A. L. Schmeltekopf, A t . Mol. Phys.

-

- 5, 1 (1969). V. Cermak, J. Chem. Phys. - 44, 3774 (1966).

D. R. Bates, Phys. 'Rev. - 77, 718 (1953).

C. B. Collins and W. W. Robertson, J. Chem. Phys. 40, 701 (1964). - 13.

U.

12.

13.

14.

B. H. Mahan and C. El. Young, J. Chem. Phys. 44, 2192 (1966).

G. M. Lawrence (private communication).

T. G. Stanger and G. Black, Stanford Research Ins t i t u t e , preprint (1971).

W. L. Borst and E. C. Zipf, Phys. Rev. A 2, 979 (1971).

R. A. Young and G. Van Volkenbwrgh, J. Chem. Phys. ( i n press).

-

15. C. A. Barth, C. W. Hord, J. B. Pearce, K. K. Kelly, G. P. Anderson, and

A. I. Stewart, "Mariner 6 and 7 Ultraviolet spectrometer Experiment,"

University of Colorado, 1971.

C. S. Weller and M. A. Biondi, P h p . Rev. Let ters 19, 59 (1967).

T. S. Wauchop and H. P. Broida, J. Geophys. Res. - 76, 21 (1971).

16.

17.

18. C. A. Barth

-

Science 165, 1~04 (1969). - 19. H. E. Hinteregger, "Absolute Intensi ty Measurements i n the Extreme

Ultraviolet Spectrum of Solar Radiation," AFCRL-65-746, Cambridge

Research Laboratory, 1965.

-7-

20. G. Herzberg, Molecular Spectra and Molecular Structure (D. Van Nostrand

Co., Lnc., Princeton, N.J.> 1950), Vol. I, pp. 200.

A. Tewarson and H. B Palmer, J. Mol. Spectry. 27, 246 (1968). 21.

-8-

s I 0 d X

In n

-ti rl d W

0 r;' 0 rf

X

8 0

-t? c- 4 v

Ln N

0'

3 0 rl X

n 0 2 +I 0 N (r, v

c N ix

I

l<

L= N

V

3

-! cc

In

0

+I rl

.

ri

W I+

0 .

n 0 0 rl

31 0 rl hl W

c N

Ix I w

IF9 cu

IA

0 2

rl

m rn 0 - 4 6 0

3 0 0

0

0

u3

(u 0 0

0 M

0 V

-9-

TABLE 11 Transit ion probabi l i t i es of CO$ ‘li“ - X measured from 0.32 nm resolution spectra. (v’,0,0) - (v’ ,3,2) t r ans i t i ons and those without brackets for (VI ,3,3) 4 (v”,o,o) .

Figures with brackets are Tor the

0.31 0.22 0.14 0.02 0.01

0.60 0.06 0.06 0.18

(0.10) . (3.19) 0

1 (0.01) (0.03) (0.07)

0.49 0.15 0.20 0.05 2 (0.01). . (0.03) (0.01) (O .Ob) ,

0.19 0.35 0.14 3.12 0.32 (0 .W (0.09) (9.05) 3

0.13 0.17 0.48 0.05 0.12 (3.04) *4

5 0.51 3.35 0.13

(b) J = 1/2

0 1 2 3 4

0.24 0.25 3.11 0.05 0.02 (3.13) (0.24)

0

0.51 3.04 0.13 0.14 0.06 ‘ (0.37) (0.04)

1

0.46 3.10 0.20 0.05 0.04 (0.03) (0.07) (3.02) (9.03)

2

0.48 3. 18 0.03 3.10 0.01 (0.10) (0.05) (0.35 3

4 0.17 0.54 0.05 0.07 0.13 ( 0 .37. )

5 0.52 0.35 0.13

-13-

TABLE I11 Quenching rates of C02, N2, He, and NO on CO( a 3E).

NO 3.2 - + 1.6 y . l O - l o 4.9 2 2.4 x

N2 v' = 0 3.8 - + 1.9 5.7 - 3. 2.8

v' 2 7.3 - + 3.6 11 - + 5.0

c02 4.8 - + 2.4 7.9 I + 4.0

He < 10-13 7 x 10-19

TABLE IV Relative popula.tions cjf NO A 2 7 and2B 2 Ji produced i n the reaction of CO(a Il) with NO(x Y) .

Electronic Relative Leve 1 V' Pooulation

0 1.09 2 A X

1 0.12

2 0.05

s2n 0 0.16

1 0.10

Ob served Relative Cross Section G a s Bands Population ( x 19-18 cm2) V1

Added

N2O N20+ (A2C - X C) 3 1.0 9.2 2

1 0.08 0.9

02 03 (b% - a.4n)- 0

1 2

co CO+ (B% - X S ) 0

1

2

co CO+ (A% - X2T: 0

1 2

3 4 5

1.0 0.06

1.3 0.42 0.12

1.0

0.75 0.73

0.78 0.93 1.0 .

3.22

0.17 0.16

4.7 0.28

1.0

0.38 0.10

0.66 0.67 0.68

0.91 1.8 2.1

0.73 0.68 3.58

F I G m CAPTIOIIJS

3 Fig. la Side view of the reaction chamber used t o study the He(2 S) and C02

flame including the He af%erglow region.

3 l b Top view of the reaction chahber f o r studying the He(2 s) and

C02 flame, and thelamp and opt ics used t o measure H(2 3 S) concentration.

Fig. 2 A 0.02 nm resolution spectrum of C02 + " 2 (A TI - '-42 X n ) between 329.0 and

365.0 nm as seen i n a C02 - He(2 3 S) flame. Similar spectra were used

t o obtain the t r ans i t i on probabi l i t i es of Cog (x - y) i n Table I. . .

Fig. 3 Spectrum of CO (a3n - xh) Cameron bands observed in recombination of

+GO$ wicth eLeotrons (0.02 m resoau-tican).

- *a FIG. 1

PUMP

I 5 cm 1

( b ) _ . . - . . ~ ,.' , ... . . , I / . .

.. .

'PHOTOMETER

FLAME

MICROWAVE CAVITY

ELIUM

0 B S E RVAT ION WIN DO W

,AMP

,

0 cv'

0 6

-

A cu 0-

T h

0 0-

0 m-

E c

0

0

I

0

FIG. 3

0 -m N

0 -m cv

c Y , APPENDIX A

INVITED LECTURES AND PAPERS

E/ 1/73 Seminar, Department of Physics, U.C.S.B. "Outsider's View of t h e Ultraviolet Spectrum of Mars" (H. P. Broida)

1/28/71 Western Spectroscopy Association Conference, Asilomar, California "Ultraviolet Spectra of Mars" (H. P. Broida) I

3/11/71 F i f t h Arizona Conference on Planetary Atmospheres, Tucson, Arizona "Cross Sections f o r the Production of Fluorescence of CO$ i n the Photoionization of Cog by 58.4 nm Radiation" (T. S. Wauchop)

"Ultraviolet Spectra of Mars'' (H. P. Broida) 3/13/71 Seminar, Department of Physics, U.C. I rv ine

,6/14/71 Molecular Spectroscopy Symposium, lumbus, Ohio "Lifetime and Quenching o f CO(a 9 ll) i n a Flowing Helium Afterglow" (T. S. Wauchop) .

PUBLISHED ARTICUS

Author

T. S. Wauchop H. P. Broida

T. S. Wauchop H. P. Broida

K. Monahan T. S. Wauchop H. P. Broida

T. S. Wauchop

i

T i t l e Journal

Absolute Measurements of Light Emission J. Quant. from CO$ i n t h e In te rac t ion of He(23S) with C02 Radiat. Transfer

Spectrosc.

( In press )

I n preparation Lifetime and Quenching of C O ( a 3?) Produced by Recombination of C02 Ions i n a Helium Afterglow 4

Cross Section Studies of Spectral Emission Produced by Interact ion of 58.4 nm Radiation with N2, CO, 02, N20 and NH3

I n preparation

Fluorescence of CO: i n t he Photoionization J. Atmos. Sciences ( In press) of C02 by 58.4 nm Radiation