Message-Id: <v01540b0cb1488d66a85a@[192.174.2.173]>
Date: Wed, 1 Apr 1998 16:41:00 -0800
To: pinhole@exploratorium.edu
From: pauld@exploratorium.edu (Paul Doherty)
Subject: Re: Another question, ozone
>Thanks Paul for your clear answer to my pressure question.
>
>I also have another question that a student raised, which I forgot to
>include in my first e-mail. Ozone molecules form naturally about 45 km
>above the earth's surface when UV light splits O2 molecules and they
>combine with O2 molecules to form O3. The student's question was why the
>ozone layer doesn't continually get thicker as this process continues.
>(Obviously, CFC's and other human chemicals are breaking down the ozone.)
>But what is the natural process that breaks down ozone molecules?
>
>On a related note, why is it that ozone only forms at that particular point
>in the atmosphere? Why not in all parts of the atm?
>
>I've tried finding answers to these questions in books, but so far without
>luck.
>
>-Geoff
Hi Geoff
UV at a wavelength near 242 nm disociates oxygen. this is in the vacuum
ultrviolet and cannot penetrate any reasonable quantity of air.
O + O2 + M = O3 + M
where M stands for any molecule is the reaction that produces ozone.
The M carries away the energy to allow the Ozone to not split apart.
Naturally ozone decomposes via the reactions
O3 + O = 2 O2
O3 + light = O2 + O
the light must have a wavelength shorter than 1134 nm (shorter than near IR.)
The amount of ozone is a balance between creation and destruction.
Paul D