Nitric oxide (NO) in the tropsphere reacts with the oxygen forming nitrogen dioxide:
`2NO + O_(2) to 2NO_(2)`
Nitrogen dioxide, in the presence of light, decomposes to NO and nascent oxygen:
`NO_(2) overset("light")to NO + [O]`
The nascent oxygen produced is highly reactive and oxiddies oxygen to ozone:
`O_(2) +[O] to O_(3)`
