The quantum efficiency of the primary processes in formaldehyde photolysis at 3130 Å and 25°C
10.1002/kin.550100706
Crossref journal-article
Wiley
International Journal of Chemical Kinetics (311)
Abstract

AbstractThe mechanism of the photolysis of formaldehyde was studied in experiments at 3130 Å and in the pressure range of 1–12 torr at 25°C. The experiments were designed to establish the quantum yields of the primary decomposition steps (1) and (2), CH2O +hν → H + HCO (1): CH2O +hν → H2+ CO (2), through the effects of added isobutene, trimethylsilane, and nitric oxide on ΦCOand Φ. The ratio ΦCO/Φwas found to be 1.01 ± 0.09(2σ) and (Φ+ ΦCO)/2 = 1.10 ± 0.08 over the range of pressures and a 12‐fold change in incident light intensity. Isobutene and nitric oxide additions reduced Φto about the same limiting value, 0.32 ± 0.03 and 0.34 ± 0.04, respectively, but these added gases differed in their effects on ΦCO. With isobutene addition ΦCO/Φreached a limiting value of 2.3; with NO addition ΦCOexceeded unity. The addition of small amounts of Me3SiH reduced Φto 1.02 ± 0.08 and lowered ΦCOto 0.7. These findings were rationalized in terms of a mechanism in which the “nonscavengeable,” molecular hydrogen is formed in reaction (2) with ϕ2= 0.32 ± 0.03, while the “free radical” hydrogen is formed in reaction (1) with ϕ1= 0.68 ± 0.03. In the pure formaldehyde system these reactions are followed by (3)–(5): H + CH2O → H2+ HCO (3); 2HCO → CH2O + CO (4); 2HCO → H2+ 2CO (5). The data suggestk4/k5≅ 5.8. Isobutene reduced Φby the reaction H +iso‐C4H8→ C4H9(20), and the results givek20/k3≅ 43 ± 4, in good agreement with the ratio of the reported values of the individual constantsk3andk20.

Bibliography

Horowitz, A., & Calvert, J. G. (1978). The quantum efficiency of the primary processes in formaldehyde photolysis at 3130 Å and 25°C. International Journal of Chemical Kinetics, 10(7), 713–732. Portico.

Authors 2
  1. Abraham Horowitz (first)
  2. Jack G. Calvert (additional)
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Dates
Type When
Created 20 years, 8 months ago (Jan. 1, 2005, 9:27 p.m.)
Deposited 1 year, 7 months ago (Jan. 17, 2024, 5:49 p.m.)
Indexed 1 year ago (Aug. 7, 2024, 4:30 a.m.)
Issued 47 years, 2 months ago (July 1, 1978)
Published 47 years, 2 months ago (July 1, 1978)
Published Online 20 years, 10 months ago (Oct. 19, 2004)
Published Print 47 years, 2 months ago (July 1, 1978)
Funders 0

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@article{Horowitz_1978, title={The quantum efficiency of the primary processes in formaldehyde photolysis at 3130 Å and 25°C}, volume={10}, ISSN={1097-4601}, url={http://dx.doi.org/10.1002/kin.550100706}, DOI={10.1002/kin.550100706}, number={7}, journal={International Journal of Chemical Kinetics}, publisher={Wiley}, author={Horowitz, Abraham and Calvert, Jack G.}, year={1978}, month=jul, pages={713–732} }