OZONE CHEMISTRY AND TECHNOLOGY

Ozone Absorption Coefficients in the Visible and Ultraviolet Regions EDWARD C. Y. INN U. S. Naval Radiological Defense Laboratory, San Francisco 24, Calif. YOSHIO TANAKA

Downloaded by UNIV OF SYDNEY on March 19, 2013 | http://pubs.acs.org Publication Date: January 1, 1959 | doi: 10.1021/ba-1959-0021.ch037

Geophysics Research Directorate, Air Force Cambridge Command, Bedford, Mass.

Research Center, Air Research and Development

A comparison is made of the ozone absorption coefficients in the visible a n d ultraviolet regions measured by the authors with those reported by Vigroux. The experimental methods are described, especially with regard to the nature of the absorbing gas, the method of measurement of absorption intensity, a n d the experimental arrangement. In general, the two sets of results agree reasonably well in the regions of the Hartley, Huggins, and Chappuis bands. In the Hartley b a n d region the agreement is much better between the authors' results a n d Vigroux's than between those of N y a n d Choong a n d either. The agreement between the authors' results a n d those of Vigroux in establishing a reliable and consistent set of ozone absorption coefficients is discussed.

W h e n t h e a u t h o r s ' results o n a b s o r p t i o n coefficients of ozone i n t h e v i s i b l e a n d u l t r a v i o l e t regions were p u b l i s h e d (1), a s i m i l a r set of r e s u l t s a p p e a r e d i n t h e l i t e r a t u r e p u b l i s h e d b y V i g r o u x (3). P r i o r t o t h i s , t h e r e s u l t s o f N y a n d C h o o n g (2) h a d b e e n a c c e p t e d as t h e best a v a i l a b l e d a t a . T h e a u t h o r s ' r e s u l t s h a v e b e e n a d e q u a t e l y c o m p a r e d w i t h these. A u n i f o r m a n d c o n s i s t e n t set of ozone a b s o r p t i o n coefficients is h i g h l y d e s i r a b l e , because these d a t a a r e i m p o r t a n t i n a t m o s p h e r i c p r o b l e m s a n d q u a n t i t a t i v e ozone technology. A c o m p a r i s o n of t h e a u t h o r s ' r e s u l t s w i t h those of V i g r o u x s h o u l d e s t a b l i s h a m o r e r e l i a b l e set of ozone a b s o r p t i o n coefficients. Experimental

Methods

T h e s c h e m a t i c a r r a n g e m e n t of t h e a p p a r a t u s u s e d b y t h e a u t h o r s f o r p r e p a r i n g a n d p u r i f y i n g ozone (4) is s h o w n i n F i g u r e 1. T h e gas p r e s s u r e i n t h e o z o n i z e r w a s k e p t b e l o w 12 c m . of m e r c u r y t o p r e v e n t o x y g e n f r o m c o n d e n s i n g i n t h e l i q u i d n i t r o g e n t r a p a l o n g w i t h t h e ozone. T h e ozone w a s p u r i f i e d b y r e p e a t e d f r a c t i o n a l d i s t i l l a t i o n i n t h e s a m p l e t r a p , s h o w n o n t h e r i g h t side of F i g u r e 1. T h u s , i n a l l m e a s u r e m e n t s a l m o s t p u r e ozone w a s u s e d . 263

In OZONE CHEMISTRY AND TECHNOLOGY; Advances in Chemistry; American Chemical Society: Washington, DC, 1959.

A D V A N C E S IN CHEMISTRY SERIES


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Figure

1. Schematic diagram of experimental arrangement for preparation a n d purification of ozone

V i g r o u x u s e d a m i x t u r e of ozone a n d o x y g e n , o z o n i z e d o x y g e n , w h i c h w a s p r e p a r e d i n a s i m i l a r w a y as t h e a u t h o r s ' . B e c a u s e n o f u r t h e r p u r i f i c a t i o n w a s m a d e , t h e gas i n these m e a s u r e m e n t s u s u a l l y c o n s i s t e d of a m i x t u r e of ozone a n d o x y g e n . T h e q u a r t z a b s o r p t i o n c e l l t h e a u t h o r s u s e d w a s 10 c m . l o n g . B e c a u s e t h i s c e l l w a s i n d i r e c t c o m m u n i c a t i o n w i t h t h e p u r i f i c a t i o n s y s t e m , t h e p u r i f i e d ozone w a s v a p o r i z e d d i r e c t l y i n t o i t f r o m t h e sample t r a p . Pressure measurements were m a d e w i t h a sulfuric acid manometer, b y a calibrated expansion method, or w i t h a mercury m a n o m e t e r , d e p e n d i n g o n t h e p r e s s u r e d e s i r e d . F o r e a c h p r e p a r a t i o n of p u r i f i e d c o n densed o z o n e , a n a n a l y s i s w a s m a d e of t h e p u r i t y b y c o n v e n t i o n a l c h e m i c a l m e t h o d s . F o r the several preparations analyzed, the p u r i t y ranged f r o m 90 to 9 5 % w i t h a n a v e r a g e of 9 2 % . I n V i g r o u x ' s m e a s u r e m e n t s , t h e ozone c o n c e n t r a t i o n i n t h e o z o n i z e d o x y g e n w a s determined b y chemical methods, f r o m w h i c h the reduced pressure was calculated for t h e p a t h l e n g t h s u s e d . T h e s e m e a s u r e m e n t s were c a r r i e d o u t f o r t h e s p e c t r a l r e g i o n f r o m 3 1 0 0 t o 3400 A . t o e s t a b l i s h a q u a n t i t a t i v e r e l a t i o n s h i p b e t w e e n r e d u c e d p r e s s u r e a n d c o n c e n t r a t i o n . I n s u b s e q u e n t a b s o r p t i o n coefficient m e a s u r e m e n t s i n o t h e r s p e c t r a l regions, t h e c o r r e s p o n d i n g r e d u c e d p r e s s u r e of ozone w a s d e t e r m i n e d b y t h i s r e l a t i o n s h i p . O n e a r m of a c r o s s - s h a p e d a b s o r p t i o n t u b e w a s a l w a y s u s e d t o o b t a i n t h e absorption s p e c t r u m i n this region—hence the reduced pressure for t h a t p a t h l e n g t h — a n d t h e o t h e r a r m w a s u s e d f o r o t h e r s p e c t r a l regions of i n t e r e s t . T h e r e d u c e d p r e s sure c o r r e s p o n d i n g t o t h e p a t h l e n g t h f o r t h e l a t t e r w a s c a l c u l a t e d f r o m t h e r a t i o of the actual lengths of t h e t w o a r m s . F o r absorption measurements, the authors used a C a r y recording spectrophotom eter i n w h i c h t h e a b s o r b a n c e s w e r e d i s p l a y e d d i r e c t l y o n a r e c o r d e r c h a r t as t h e d i f f e r ent s p e c t r a l regions w e r e s c a n n e d . I n t h i s i n s t r u m e n t , t h e a b s o r p t i o n c e l l is l o c a t e d between the exit slit a n d p h o t o m u l t i p l i e r tube detector, thus m i n i m i z i n g a n y p h o t o c h e m i c a l effect d u r i n g t h e m e a s u r e m e n t . C o r r e c t i o n s were a p p l i e d t o t h e r e c o r d e d a b sorbances f o r a n y ozone d e c o m p o s i t i o n d u r i n g t h e t i m e of m e a s u r e m e n t . V i g r o u x used photographic methods to obtain the absorption spectrum w i t h the m e d i u m H i l g e r spectrograph. T h e absorption intensity was obtained b y conventional m e t h o d s of p h o t o g r a p h i c p h o t o m e t r y . I n photographing the spectrum, the absorption c e l l w a s p l a c e d b e t w e e n t h e l i g h t s o u r c e a n d slit of t h e s p e c t r o g r a p h , t h e a b s o r b i n g gas b e i n g e s s e n t i a l l y e x p o s e d t o t h e f u l l b e a m of t h e l i g h t source. T h e t w o e x p e r i m e n t a l m e t h o d s h a v e b e e n d e s c r i b e d i n d e t a i l (1, 3, 4)·


INN A N D TANAKA—ABSORPTION

Comparison of

265

COEFFICIENT

Results

I t is c o n v e n i e n t t o discuss t h r e e regions o f t h e a b s o r p t i o n s p e c t r u m , s e p a r a t e l y : t h e H a r t l e y b a n d f r o m 2000 t o 3000 Α . , t h e H u g g i n s b a n d f r o m 3000 t o 3500 Α . , a n d t h e C h a p p u i s b a n d f r o m 4000 t o 7500 A . T h e r e s u l t s of t h e ozone a b s o r p t i o n c o efficients m e a s u r e m e n t s a r e d i s p l a y e d i n F i g u r e s 2, 3, a n d 4, r e s p e c t i v e l y . T h e a b s o r p t i o n coefficients m e a s u r e d b y t h e a u t h o r s a r e t a b u l a t e d i n T a b l e I . T a b l e I.

Absorption Coefficients of O z o n e

In Hartley Band Region


Wave length, A. 2002 12 22 32 42 52 62 72 82 92 2102 12 22 32 42 52 62 72 82 92 2202 12 22 32 42 52 62 72 82 92 2302 12 22 32 42 52 62 72

k, Wave c m . , length, base 10 A -1

3.74 3.70 3.63 3.71 3.83 4.02 4.36 4.85 5.22 5.82 6.39 7.18 8.09 9.20 10.3 11.7 13.1 14.6 16.5 18.3 21.0 23.0 25.4 28.4 30.9 34.3 37.6 40.9 44.8 48.9 52.8 56.6 60.6 64.8 69.2 73.6 78.2 83.2

82 92 2400 02 12 22 32 38 44 52 58 63 72 78 82 90 92 2500 08 19 27 39 43 53 62 66 71 75 79 87 97 2604 17 24 35 43 50 54

k, cm. , base 10 - 1

86.2 90.1 93.7 95.3 98.9 103 107 111 112 116 118 118 122 124 123 127 127 130 127 133 130 134 130 135 132 127 131 130 128 133 126 128 121 123 114 118 112 111

In Chappuis Band Region

k, Wave length, c m . , base 10 A. - 1

62 69 75 82 2692 95 2702 12 18 22 32 42 46 52 62 72 82 92 2802 12 22 30 42 52 62 72 82 92 2902 12 22 32 42 52 62 72 82 92

108 102 103 96.7 95.4 94.6 89.1 84.3 84.4 79.9 75.4 68.6 69.3 66.6 60.6 56.8 52.4 48.4 43.6 39.7 36.4 35.2 30.4 27.5 24.3 22.2 19.3 17.4 15.5 13.5 12.3 10.7 9.44 8.33 7.25 6.32 5.52 4.78

Wave length, A. 4342 4443 4543 4629 4644 4685 4746 4838 4883 4951 5055 70 5123 60 5265 5344 5371 5397 5476 5528 5581 5685 5763 89 5841 5893 5945 5997 6038 6101 6205 6309 6413 6517 6622 6726 6832 6937 7042 7146 7250 7353 7456 7560

k, cm. , base 10 0.0007 0.0014 0.0016 0.0037 0.0037 0.0033 0.0044 0.0089 0.0077 0.0093 0.017 0.018 0.016 0.018 0.024 0.031 0.031 0.031 0.035 0.038 0.040 0.049 0.052 0.051 0.048 0.047 0.048 0.054 0.055 0.052 0.045 0.039 0.033 0.027 0.023 0.018 0.014 0.011 0.0088 0.0072 0.0057 0.0046 0.0046 0.0038 1

In Huggins Band Region

Wave length, A. 3002 13 23 34 44 54 63 75 86 96 3107 11 17 28 30 34 38 46 48 51 55 59 67 70 72 76 79 90 94 98 3200 01 05 11 15 21 24 27 39 41 45

Wave k, k, cm. *, length, cm. , base 10 base 10 A. 0.210 4.59 3249 0.171 3.71 53 3.23 55 0.177 2.83 69 0.096 2.50 72 0.117 2.18 76 0.107 1.98 80 0.152 1.66 95 0.061 1.53 3300 0.058 1.24 04 0.088 1.13 08 0.077 1.09 12 0.102 0.98 27 0.035 0.85 33 0.047 0.80 39 0.070 0.84 54 0.023 0.76 58 0.022 0.62 65 0.033 0.64 67 0.032 0.60 72 0.045 0.64 86 0.017 0.59 92 0.016 0.47 96 0.021 0.49 98 0.019 0.47 3401 0.025 0.50 18 0.0092 0.45 21 0.011 0.33 25 0.0092 0.38 30 0.013 0.36 35 0.012 0.38 39 0.016 0.37 53 0.0079 0.30 57 0.0094 0.234 62 0.0080 0.223 68 0.0054 0.290 72 0.0071 0.253 83 0.0032 0.277 88 0.0030 0.146 95 0.0047 0.0032 3507 14 0.0047 0.160 24 0.154 0.0030 1

H a r t l e y B a n d . F o r t h e r e g i o n f r o m 2000 t o 3000 Α . , a p l o t of N y a n d C h o o n g ' s results h a s b e e n i n c l u d e d i n F i g u r e 2 . I n g e n e r a l , t h e r e is f a i r l y g o o d a g r e e m e n t b e t w e e n t h e r e s u l t s of V i g r o u x a n d t h e a u t h o r s , e s p e c i a l l y i n t h e r e g i o n of t h e w i n g s of the b a n d . T h e results of N y a n d C h o o n g are consistently higher, ranging f r o m a few to 2 0 % higher t h a n t h e authors' a n d almost consistently about 2 0 % higher t h a n V i g r o u x ' s . B e c a u s e N y a n d C h o o n g ' s r e s u l t s a r e c o n s i s t e n t l y t o o h i g h , t h e y a r e less acceptable. T h e discrepancies between t h e results of V i g r o u x a n d t h e authors l i e m o s t l y i n t h e r e g i o n of t h e a b s o r p t i o n m a x i m u m . V i g r o u x ' s v a l u e s a r e a b o u t 1 0 % l o w e r t h a n t h e a u t h o r s ' i n t h i s r e g i o n a n d t h e d i s c r e p a n c y a p p e a r s t o o r i g i n a t e a t t h e p o i n t s of i n flection of t h e b r o a d c o n t i n u u m a t a b o u t 2350 a n d 2700 A . D i s r e g a r d i n g t h e d i s c r e t e bands i n this region, the u n d e r l y i n g c o n t i n u u m m a y be examined. F o r example, i f the l a t t e r i s t r a c e d s t a r t i n g f r o m t h e l o n g w a v e l e n g t h w i n g of t h e c o n t i n u u m , a n a b r u p t d i s p l a c e m e n t i s n o t e d a t a b o u t 2700 A . T h e r e is n o evidence of a s i m i l a r d i s p l a c e m e n t



266

ADVANCES

IN

CHEMISTRY

SERIES

i n t h e s h a p e of t h e c o n t i n u u m i n e i t h e r t h e a u t h o r s ' o r N y a n d C h o o n g ' s r e s u l t s . S u c h displacement is rather u n u s u a l i n a b s o r p t i o n c o n t i n u a , a l t h o u g h i t is observed where two or more continua are superposed. T h e displacement m a y be explained o n the basis o f r a p i d l y c h a n g i n g s p e c t r a l s e n s i t i v i t y o f t h e p h o t o g r a p h i c e m u l s i o n , because m o s t e m u l s i o n s , unless s p e c i a l l y s e n s i t i z e d , e x h i b i t s u c h a c h a r a c t e r i s t i c a t a b o u t t h i s w a v e l e n g t h . I f t h e s h a p e of t h e c o n t i n u u m o n V i g r o u x ' s c u r v e w e r e d r a w n i n , t h e r e w o u l d be r e m a r k a b l y good agreement throughout t h e spectral region between i t a n d the authors' curve, certainly within experimental error. F o r t h e discrete bands i n this region, t h e a b s o r p t i o n intensities are somewhat greater i n V i g r o u x ' s results t h a n i n t h e authors'. T h i s is u n d o u b t e d l y due t o t h e b e t t e r d i s p e r s i o n a n d r e s o l u t i o n of h i s s p e c t r o g r a p h . H o w e v e r , t h e differences a r e s m a l l a n d d o n o t cause a serious d i s c r e p a n c y . T h e r e s u l t s o f t h e a u t h o r s seem m o r e a c c e p t a b l e a n d a r e t h e best v a l u e s i n t h i s r e g i o n f o r t h e a b s o r p t i o n coefficient o f ozone. H u g g i n s B a n d . F i g u r e 3 shows t h e a b s o r p t i o n coefficients i n t h e r e g i o n f r o m 3000 t o 3500 A . A g a i n , t h e r e i s g o o d a g r e e m e n t b e t w e e n t h e r e s u l t s of t h e a u t h o r s a n d V i g r o u x , especially f o r t h e c o n t i n u u m u n d e r l y i n g t h e discrete bands. T h i s is r e m a r k a b l e because t h e a b s o r p t i o n coefficient changes a b o u t 2 0 0 - f o l d w i t h i n a s p e c t r a l r e g i o n of 5 0 0 A . d e s p i t e t h e d i s t i n c t differences i n t h e e x p e r i m e n t a l m e t h o d s . T h e r e a r e s i g n i f i c a n t differences i n t h e i n t e n s i t i e s of t h e d i s c r e t e b a n d s l y i n g a b o v e the c o n t i n u u m . Because this results f r o m spectral resolution a n d dispersion, V i g r o u x ' s r e s u l t s a r e m o r e a c c e p t a b l e a n d r e p r e s e n t t h e best v a l u e s i n t h i s r e g i o n . F u r t h e r m o r e , V i g r o u x ' s m e a s u r e m e n t s (3) o n t h e change i n a b s o r p t i o n coefficient w i t h t e m p e r a t u r e i n t h i s r e g i o n a r e of great i m p o r t a n c e i n e s t a b l i s h i n g a r e l i a b l e set of a b s o r p t i o n c o efficients a p p l i c a b l e t o s p e c t r o s c o p i c m e a s u r e m e n t s of a t m o s p h e r i c ozone. C h a p p u i s B a n d . F i g u r e 4 shows t h e a b s o r p t i o n coefficients of ozone i n t h e r e g i o n f r o m 4000 t o 7500 A . A g a i n t h e r e i s g e n e r a l a g r e e m e n t b e t w e e n t h e a u t h o r s ' results a n d V i g r o u x ' s . T h e v e r y l o w a b s o r p t i o n coefficients i n t h i s r e g i o n m a d e m e a s u r e m e n t s e s p e c i a l l y d i f f i c u l t . A l t h o u g h t h e r e l a t i v e differences b e t w e e n t h e a u t h o r s ' r e s u l t s a n d V i g r o u x ' s seem l a r g e f o r c e r t a i n regions i n t h e a b s o r p t i o n b a n d , t h e a b s o l u t e differences a r e s m a l l . T h e r e is good agreement between the results f o r the l o n g wave l e n g t h w i n g of t h e



INN

267

A N D TANAKA—ABSORPTION COEFFICIENTS

3000

3100

3200 WAVE

Figure 3.

3300 LENGTH A.

3400

3500

Absorption coefficients of ozone in region of the Huggins b a n d , 3000 to 3500 A . — Authors results • Vigroux's results 7

• •

-

•1 \ J

•I

v/

-

ο

ι 4000

y ·

Figure 4.

1

I 5000

1 I

I 6000 WAVE LENGTH

1 I A.

1 7000

1 1

1 8000

Absorption coefficients of ozone in region of Chappuis b a n d , 4000 to 7500 A. — Authors' results Φ Vigroux's results


A D V A N C E S IN CHEMISTRY SERIES

268

band, except at the extreme long wave length e n d , w h i c h is n o t too i m p o r t a n t . There is a m o r e s i g n i f i c a n t difference a t t h e m a x i m u m a n d t h e s h o r t w a v e l e n g t h w i n g , e s p e c i a l l y f o r t h e o v e r l y i n g diffuse b u t d i s c r e t e b a n d s . B e c a u s e o f t h e b r o a d n e s s of t h e diffuse b a n d s , r e s o l u t i o n a n d d i s p e r s i o n m a y n o t a p p r e c i a b l y b e r e s p o n s i b l e f o r t h e difference. T h e difference p r o b a b l y r e s u l t s f r o m t h e i n h e r e n t difficulties i n m e a s u r i n g a b s o r p t i o n f o r s u c h a w e a k l y a b s o r b i n g b a n d . A s t h e r e s u l t s agree w i t h i n 1 0 % t h r o u g h o u t m o s t of t h e r e g i o n , i t i s sufficient t o a c c e p t a n a v e r a g e of t h e t w o r e s u l t s unless a n a b s o r p t i o n coefficient w i t h a b e t t e r a c c u r a c y i s r e q u i r e d .


Conclusion T h e satisfying agreement between the authors' results a n d V i g r o u x ' s for t h e a b s o r p t i o n coefficients of ozone i n t h e regions f r o m 2000 t o 3500 A . a n d f r o m 4000 t o 7500 A . c o n s i d e r a b l y s t r e n g t h e n s t h e e s t a b l i s h m e n t of a c o n s i s t e n t set o f d a t a . T h i s a g r e e m e n t w a s o b t a i n e d d e s p i t e t h e d i s t i n c t differences i n t h e e x p e r i m e n t a l m e t h o d s a n d t h e r e b y s u p p o r t s t h e v a l i d i t y a n d a c c u r a c y of t h e r e p o r t e d d a t a . O n t h e basis of these c o n s i s t e n t r e s u l t s , t h e a p p l i c a t i o n of r e l i a b l e s u p p o r t i n g a b s o r p t i o n coefficient d a t a t o a n y ozone m e a s u r e m e n t w i l l p l a c e g r e a t e r confidence o n t h e d e r i v e d q u a n t i t a tive results. Literature C i t e d (1) Inn, E. C. Y., Tanaka, Y., J. Opt. Soc. Am. 43, 870 (1953). (2) N y , T.-Z., Choong, S.-P., Chinese J. Phys. 1, 38 (1933); Compt. rend. 195, 309 (1932); 196, 916 (1934). (3) Vigroux, E., Ann. Phys. 8, 709 (1953). (4) Watanabe, K., Zelikoff, M., Inn, E. C. Y., Air Force Cambridge Research Center, Cambridge, Mass., AFCRC Rept. 53-23 (June 1953). RECEIVED for review M a y 27, 1957.

Accepted June 19, 1957.


OZONE CHEMISTRY AND TECHNOLOGY

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