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• Direct Measurements of the Reaction H+CH2O → H2+HCO by means of V-UV Detection of Formaldehyde behind Shock Waves

G. Friedrichs, D.F. Davidson, and R.K. Hanson
Int. J. Chem. Kinet. 34, 374-386 (2002)

 

The combination of sensitive detection of formaldehyde by 174 nm absorption and use of ethyl iodide as a hydrogen atom source allowed direct measurements of the reaction H+CH2O → H2+HCO behind shock waves. The rate constant was determined for temperatures from 1510 to 1960 K to be:

k2 = 6.6· 1014 · exp(-40.6 kJmol-1 / R T) cm3mol-1s-1 (Δ log k2 = ±0.22)

Considering the low uncertainty in k2, which accounts both for experimental and mechanism-induced contributions, this result supports the upper range of previously reported, largely scattered high temperature rate constants.

V-UV light of 174 nm was generated by a microwave N2 discharge lamp. At typical reflected shock wave conditions of 1750 K and 1.3 atm, as low as 33 ppm formaldehyde could be detected. High temperature absorption cross sections of CH2O and other selected species have been determined.

 

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