Peroxyacyl nitrates (PANs) are secondary pollutants in photochemical smog. Free radical reactions catalyzed by ultraviolet light from the sun oxidize unburned hydrocarbons to aldehydes, ketones, and dicarbonyl compounds, whose secondary reactions create peroxyacyl radicals, which combine with nitrogen dioxide to form peroxyacyl nitrates. These dissociate only slowly into radicals and NO2 , which means that they can carry nitrates to sites other than their place or origin to regions in the troposphere where ozone can be produced more readily. Peroxyacyl nitrates are both toxic and irritating and even dissolve more readily in water than ozone. Even a few parts per billion can cause eye irritation and higher concentrations can cause extreme damage to vegetation.

a)One of the highest concentrations of peroxyacyl nitrates has been found in the Los Angeles (LA) basin at 30 ppb, reaching its peak at mid-afternoon. Most of the pollution in the LA basin is created in an area of only 3000 km^2 and the pollution depth below the inversion layer is normally about 500 m . This concentration was therefore found in 1500 km^2 f air above Los Angeles

b) Peroxyacyl nitrates contain two relatively weak bonds that can be broken by low-energy photons. The weakest is the N-O bond in the nitrate functional group of the molecule with a standard bond-dissociation energy of 201 kj/mol . What is the longest wavelength of a photon, in nanometers, that has enough energy to cause the photodissociation of the weakest bond. Assume all energy of the photon is efficiently used for the photodissociation.