ULTRAVIOLET ABSORPTION CROSS-SECTIONS

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ULTRAVIOLET ABSORPTION CROSS-SECTIONS

OF HALOCARBONS OF STRATOSPHERIC INTEREST

D. GILLOTAY and P.C. SIMON

Institut d'Aeronomie spatiale de Belgique Avenue Circulaire, 3, B-1180 Brussels, BELGIUM.

and

A. DE RUDDER

National center for Atmospheric Research Boulder, CO 80307, USA

1. Introduction.

The spectrometry laboratory of the "Institut d'Aeronomie Spatiale de Belgique" (IASB) is involved, since more than twenty years, in the measurements of ultraviolet absorption cross-sections of atmospheric constituents.

Measurements of temperature dependence of absorption

cross-sections and calculations of photodissociation coefficients have been realised since 1971 for about thirty halocarbons of stratospheric interest. Recently, an updated compilation of the absorption cross-sections of halocarbons, entitled: "Ultraviolet Absorption Cross-sections of photoactive species of stratospheric interest, Part 1 : The Halocarbons.

^1I

has been published by Gillotay and Simon (Aeronomica Acta A 356, 1990).

The purpose of this brief report is to present some recent results concerning absorption cross-sections measurements of halocarbons and to compare them with other available data.

Recent values of Ozone Depletion Potential and lifetime calculated with a 1-0 model will be also presented.

2. Experimental.

Absorption cross-sections are measured between 170 and 300 nm by means of a double beam experimental device equipped with

thermostatic absorption cells of 20 and 200 cm. The experimental temperatures range from 210 to 295 K. A detailed description of the experimental system is given in Gillotay et al.,(Planet. Space

sci., 37, 1127-1140, 1989).

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An error budget for the absorption cross-sections measurements is presented in table 1.

Tablo: I. Error budgel (a)T-;:9SK

OplicaJ patll (100=

=

^0.1^ani

I'n:s.sure (iD tIIr I2np: 10'-:: " 10-' lorr) Impurities iD the _pie

Tcmper.lIure (=0.1 K al 300 K) Abscrbam::r m(I .. 1) for r - I TOLaI r.II .... OTTor (::.,) (b) T-::IOK

Optical patll (200 CID l: 0.1 an)

~UR (in tile I2.lIge 10'-2" 10-] lorr) Impuritic:s iD the souaplo:

Tempel2lure 1::!:1 K al 210 K)

Crou-lCI:lioll dependence 011 IemPC121urc ttTor Abscrbam::r m(l.,.,) for ^{t -} I

-0.6

(lmn. value consicUrtd)

TOIaI r.m.s. error (2.,)

.'

^'0

^.

^'0

O.OS 0.1 0,1 0,03 ::.0

=1.00

o.OS 0.1 0.1

::.0

J.J

l: 2.47 =3.62

(From Simon et al., J. Atmos. Chern., 2, 103-135, 1988)

3. Results.

Figure 1. represents the relative absorption cross-sections values obtained for CFC-11 by 6 different groups. The agreement between all the measurements is relatively good (within ± 10 %) up to 230 nm. A comparison of temperature dependence measurements show the same agreement.These conclusions are also valid for of CFC-12, CFC-113, CFC-114, CFC-115. (see Simon et al., J. Atmos. Chern., 2, 103-135, 1988; and Simon et al., Ann. Geophysicae, Q, 239-248, 1988)

Figure 2.1-2.3 represent a similar comparison for three alternative HCFC, the disagreement between the four sets of data is, in all cases, very large at room temperature and more important for absorption cross-sections values obtained at low temperature.

(Gillotay and Simon, accepted by J. Atmos. Chern, 1990).

These two examples show the need for further and more accurate

determinations of the photolytic parameters of photoactive

atmospheric constituents.

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Z 0

M _en

rh en 0 0::

U

~ ~

0::

CFQ3 1.3

1.2 1.1 _, • ^,

1 .

0.9

0.8 0.110 180 190 ²⁰⁰ 210 220 230

WAVELENGTH (run)

Figure 1 • Relative absorption cross-sections of CFCl3 at roO'll1 temperature, as a

~unction

of wavelength.

1. 3

L2

Ll

1

0.9

0.8 Robbins, 1976 Chou et al., 1977

( * )

( - x - - ) ( - -0- - ) (--.---) (-

.... ^- ^-)

Ref.

Molina and Rowland, 1974 Bass and Ledford, 1976 M6rienne et al., 1990 Simon at al., 1988a

~-CHC12

- HCFCl23

; ;

· ⁱ

i

j

i

1

,

; I I

, , I ,

·

^I

1 : i ^I

~--.l

^• ^! ^....-&.---

^I ⁱ

ⁱ

I

, , . , . -... I

i

! '"

I~ 't-.... l~,

;

i

I :

:

!

i

,

;

,

I:

I ~.

^I

'Jr"'" i\

^,I

I ^... ^..

^.;

I ⁱ ~~ --..l' \ : _,

ⁱ

' I

;

. ^,

\:

190 200 210 220 230

WAVELENGTH (run)

._---

--

240 Figure

~.

Relative absorption cross-sections of

CF3-~~l2

at roO'll1 temperature, as a function of

wavel~.

'

( * )

(---0---) (-.-x-.-) Ref..

Allied-Signal Corporation, 1989 Molina and Molina, 1989

Orlando at al., 1990

Gillotay and Simon, 1990

(4)

Z 0

Ul

B

V,j

0 ~

~

~ ~

0::

Z 0

Irl

V,j

ta 0 0

0::

g:

~ ~

CHJ.CF02 • HCFC·141b L3

--.- -

L2

^.~^..

---

L1

^I^I

-

"

f 1

:",' :'... 1 ;

,f

" . .,'--- l

0.9 . ,

~.,i~

j

0.8 0.7so 190 200 210 220 230

WAVELENGTII (run)

Figure

~.

Relative absorption cross-sections of CH]-CFC12 at room temperature, as a function of wavelength.

1.3 -.,

\

( * )

(---0---)

(-.-x-.-) Ref .•

:

,

Allied-siqnal Corporation, 1989 Holina and HOlina, 1989

Orlando et al.,

1990

Cillotay and simon, 1990

CHJ.Cf2Q -

HCFC142b

i

^~:

i 1

240 L2

^~

^.. / ^, .--i-i-~_1~- ^" ⁱ .. -

\. ^-

^{: , I}

i1

L1

1

0.9

0.8 i \ i

..

,

.

^/ ^;I: ^• ^I

~'~\ . • ',..A'

^t ^\

I

!

^\1

:x:-; ^.. ^\' ^:' ⁱ :

^I

...

^{.. :It}

^, ⁱ

l"' ... ^lf'#" ^;

I

. .~.

~~

...

. ⁱ ( i ^.

!

ⁱ_I

:

I

ISO 190 210 220

WAVELENGTH (run)

Figure

~.

Relative absorption cross-sections of _CH]-C:2 Cl at room temperature, as a function of

wavelen~.

( * )

(---+---) (-.-x-.-) Ref.

Allied-Signal Corporation, 1989 Hubrich and Stubl,

1980

orlando et al., 1990 Cillotay and Simon, 1990

230

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t-3

QI

0'

I-'

a. a 0 0

('I) ('I)

0-

('I)

rt

QI

rt "0

('I) rJl QI

...

('I) N

Ozone Depletion Potentials.

11 C

1-" ('I)

a 11 ::s rt '"'1

1-" ('I) ('I) 1-" 1-"

::s a. a. 0 ::s

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rt

('I)

0 a.

('I)

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11

('I)

0 rt a

1-'-

0 § ::s 0 'i:1 .. 0 rt

I-' ('I) \0

::s

\0

rt

0 1-'- QI I-'

11

('I)

0 "0

Hl

a 11 ::r: rt

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0

..." QI

11 g ::s

rJl

l-D Model 2-D Model LLNL AER Du Pont Montreal Wuebbles lASB Oslo LLNL AER Du Pont CrCIl (crcI..) 1.8 1." 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 crC12 (CF.CI.) 1.8 8.92 1.8 1.8 1. 83 8.93 8.92 8.87 8.88 8.89 CrCll3 (C.F.CI.) ".82 8.83 8.89 8.8 8.8 8.89 8.86 8.76 CrCl14 (c.r

4

Cl.) 8.76 8.63 8.79 1.8 8.75 8.76 8.82 8.56 CrC1l5 (c.r,cl) 8.43 ",36 8.45 8.6 8.42 8.42 8.48 8.27 8.37 HcrC21 8.812 HCrC22 8.845 8."49 8.1144 8.834

11.046

8.847 8.857 8.843 "CrC123 1"813 8.816 8.813 8.888 8,813 8.817 IJ.P22 8.817 HcrC124 8,lU6 8.818 IJ.IU 7 o ,lU8 8.819 ".824 8.817 HcrC14lb 8.869 8.878 8.869 8.841 8.P89 8.889 8.11 8.888 HCrC142b 8.851 8. "t,8 8.855 8.835 8.056 8.858 8.862 11.847 CCh 1.1 1.16 1.1 1. 8" 1.2 1.1 8.95 1.2 CIICI

~

O.Oil5 C1t.C1. 8.089 ClhCCh 8.894 8.12 8.892 8.857

IJ. 14

8.]3 8.16 8.149

C~H,.C1

8.,,86 Halon 1211 (Cr.BrCI) 2.7 3.8 2.2 4.9 Halon 1381 (Cr.Br) 11. 4 10.8 13.2 8.8 Halon 2402 (C.r

4

Br.) T.B.D. 6.2 6.9 Halon 22b1 (CHF.Br) 0,40

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(6)

Lifetimes (years).

. I-D Hodel 2-D Hodel

LLNL

AER

Du Pont

lASH'"

Oslo LLNL

AER

CFCll (CFCh) 80 60 71 89 60 52 t.7

CFC12 (CFaCla) 154 125 154 15B 105 101 95

CFCllJ (C aF

2

Ch) 96 96 117 139 101 79

CFC1l4 (CaF .. Cla ) 209 2611 319 297 236 197

CFC115 (CaF;sCl) 680 6911 548 8311 522 393 399

HCFC21 1.6

HCFC22 20 20 16 13

17

15 24

HCFC12J 1.9 2.1 1.6 1.4 1.7 1.5 2.4

HCFC124 8.4 8.8 6.9 7.4 6.5 Ie

HCFC141b B.9 9.4 7.8 6 B.e 6.9 11

HCFC142b 25 25 19 15 21 19 28

CC1 .. 7J 53 61 73 52.2 47 4e

CHCh 11.5

CH.aCl:a 1.0

CH",CCh 7.4 7.4 6 5 6.3 5.8 7.9

C",H.,Cl 1.4

Halon 1211 tCFaBrCl) 2e 49

Halon 1301 (CF:lBr) 90 86

Halon 2?'..,2 (CaF .. Bra) 45

Halon 22bl (CHF.Br) 20

HFCl25 37 37 25 27 43 19

HFC1J4a 21 21 16 15 24 12.5

HFC143a 54 52 42 411

HFC152a 2.1 2.3 1.7 1.5 2.7 1.3

Table 3. Lifetime of Halocarbons. (adapted from WMO, 1990, report 20)

where AER : Atmospheric and Environmental Research Inc.

Du Pont : Du Pont Central Research.

LLNL Oslo IASB

Lawrence Livermore National Laboratory.

University of Oslo.

Institut d'Aeronomie Spatiale de Belgique.

Du Pont 46 118

12.7 1.2 5.3 5.8 15.1 40

4.7 In conclusion, it is of fundamental importance to determine with a maximum of accuracy, the basic photolytic parameters of the photoactive atmospheric constituents in order to be able to

determine the impact on ozone budget of these compounds with a maximum reliability and to reduce the uncertainties in the model predictions on ozone depletion.

ULTRAVIOLET ABSORPTION CROSS-SECTIONS