Dye Laser Photolysis of n-Pentanal from 280 to 330 nm

Abstract

The UV photolysis of n-pentanal in the 280−330-nm region has been studied in 5-nm intervals by using dye laser photolysis in combination with cavity ring-down spectroscopy. Absorption cross sections of n-pentanal were measured at each wavelength studied. n-Pentanal exhibited a broad, structureless absorption band similar, in appearance, to that of previously studied short-chain aldehydes. The absorption spectrum peaked at 295 nm with a cross section of (6.56 ± 0.17) × 10-20 cm2 molecule-1. The formation of the HCO radical, which is a photodissociation product, was monitored in these experiments. The HCO yield was found to be independent of n-pentanal pressure (2−18 Torr) and total pressure (8−480 Torr) except for 325- and 330-nm photolysis where the size of the HCO signal was small and the dissociation was near the threshold. The dependence of the HCO radical yield on the photolysis wavelength was determined. The HCO yields were 0.058 ± 0.006, 0.095 ± 0.009, 0.10 ± 0.02, 0.14 ± 0.01, 0.10 ± 0.02, 0.15 ± 0...