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On the other hand, in winter the Λ and solar altitude curves have much the same shape, and the maxima attained are sharply dependent on latitude. 5 and i = 2, these two factors cancel, whereupon a t ζ — 0 this equation reduces to Λ = io\T ax, and even a t ζ — 20°, Λ is within a few per cent of J 0xT ax. Since most of the ozone responsible for T ax is in the upper atmosphere, this means, if these values of g and i are correct, 0600 0800 1000 1200 Ρ 1400 1600 1800 ST F I G . 1 3 . R a t e of change in actinic irradiance in t h e lower a t m o s p h e r e .

7 in the ultraviolet. Addition of w a t e r vapor does n o t affect t h e yield in the visible b u t increases t h a t in t h e ultraviolet t o 4 . OZONE τ ι 49 1 — ι 1 — ι — ι — ι — ι 5000 5500 6000 6500 1 — ι η 7000 7500 F I G . 2 0 . A b s o r p t i o n of visible solar radiation b y o z o n e in the lower a t m o s p h e r e . values as high as 130. Chain reactions, longer in the presence of water vapor, are thus indicated in the ultraviolet, but not in the visible. T o explain these observations, a p r i m a r y photodissociation of ozone by both visible and ultraviolet radiation has been proposed, with t h a t in the ultraviolet leading to more energetic products which are able to 3 2 , 1 9 0 3 8 1 4 03 ' ' Energetically, the only possible photodissociainitiate c h a i n s .

This means t h a t while the calculated life of a free and uninflu4 enced 0 2 OS^ ") molecule is some 7 sec, in air a t atmospheric pressure its life with respect to a return to the normal state m a y not be greater 5 - 4 t h a n 1 0 - to 1 0 sec. 175 150 125 ioo\ 1 50 25 0 0 1 2 Internucleor Distance, A 3 F I G . 1 8 . E l e c t r o n i c s t a t e s of t h e o x y g e n m o l e c u l e . P o t e n t i a l e n e r g y as a f u n c t i o n of internuclear distance for s t a t e s of the O 2 m o l e c u l e b e l o w 8 e v .