Investigation of the loss processes for peroxyacetyl nitrate in the atmosphere: UV photolysis and reaction with OH

The UV absorption cross sections of peroxyacetyl nitrate (PAN), CH 3 C(O)O 2 NO 2 , have been measured as a function of temperature (298,273, and 250 K) between 195 and 345 nm using a diode array spectrometer. The absorption cross sections decrease monotonically with increasing wavelength. The cross sections also decrease as the temperature is lowered. Upper limits for the rate coefficients for the reaction of OH with PAN at atmospheric temperatures were determined to be < 3 × 10 −14 cm 3 molecule −1 s −1 using the pulsed photolysis laser induced fluorescence technique. Photolysis becomes the most important atmospheric loss process for PAN above ∼7 km, and the OH reaction is found to be unimportant throughout the troposphere. These results are compared with previous measurements, and the significance of the revised values on the atmospheric loss rates of PAN is discussed.