Photochemistry of acetone under tropospheric conditions

The absorption cross sections of acetone were measured between 215 and 350 nm over the temperature range of 235 to 298 K using a diode array spectrometer. The quantum yield for the photodissociation of acetone was measured as a function of pressure at nine discrete wavelengths between 248 and 337 mn. At wavelengths longer than 270 nm, the quantum yields were found to decrease with increasing pressure in accordance with the Stern-Volmer mechanism. The zero pressure quantum yield was found to increase as the wavelength decreased and reached a value of unity near 290 nm. The quantum yields at 308 nm were found to be nearly independent of temperature between 298 and 195 K. These results were used to calculate an expression for the variation of the acetone photodissociation quantum yield with pressure and wavelength. The calculated atmospheric photolysis lifetime of acetone shows the photolysis to be the main loss process for acetone in the upper troposphere, while reaction with the OH radicals dominates its loss rate near the Earth's surface. (C) 1998 Elsevier Science B.V. All rights reserved.