Quantum Yield of CO from the Photolysis of Aliphatic Carbonyls: Implications for the Photochemical Stability of Organic Aerosols

ADAM P. BATEMAN (1), Joshua E. Klobas (1), Sergey A. Nizkorodov (1)

(1) University of California, Irvine

     Abstract Number: 158
     Last modified: April 26, 2010

Abstract
The photochemical stability of undecyl aldehyde (UA), a representative semivolatile organic aerosol compound, has been investigated using photodissociation action spectroscopy. Photodissociation action spectroscopy measures the rate of production of volatile products (CO) from photolysis of thin films of organic material (UA) as a function of the UV irradiation wavelength. The CO molecules are sensitively and quantitatively detected by cavity ring-down infrared spectroscopy (IR-CRDS). The results were consistent with the production of CO by the well-known Norrish type 1 photocleavage of the carbonyl group in UA. Using 2-nitrobenzaldehyde as a chemical actinometer, the quantum yield of CO from the photolysis of UA, i.e., the number of CO molecules generated per each photon absorbed by UA was quantified. The resulting absolute photodissociation action spectrum for UA is compared with the corresponding spectrum of secondary organic aerosol (SOA), which is known to be rich in carbonyls. This information can be used to estimate rates and determine the atmospheric importance of photochemical reactions involving organic carbonyls inside SOA particles.