The Photolysis of Acetaldehyde Under Atmospheric Conditions

Abstract

The photodecomposition of mixtures of 100–200 ppm CrLCHO in 1 atm of air or purified N2 has been studied at 300 K and the quantum yields of CO and CH, determined in the spectral range 250–340 nm. The quantum yields are nearly identical in both systems. øCo increases monoton-ically from zero at 330 nm to near 0.8 at 250 nm. øCH4 remains near zero at λ > 285 nm and increases sharply to 0.5 at 250 nm. A pressure dependence of øCo was observed at 313 nm, indicating that some quenching occurs. No H2 was observed. Quantum yields for both primary steps $$ C{H_{3}}CHO{\kern 1pt} \to {\kern 1pt} C{H_{3}} + CHO\quad {\phi _{1}} $$ $$ \to C{H_{4}} + CO\quad {\phi _{2}} $$ are derived. Measured CO production rates in sunlit CH3CHO/Air and N2 mixtures produce noontime dissociation rates of 3 × 10–6 sec-1 at 30° zenith angle. This is a magnitude lower as the currently accepted vallue of Meafher et al. (1976)KeywordsQuantum YieldZenith AngleActinic FluxAldehydic HydrogenPhotodissociation CoefficientThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.