ESR spectra of free radicals formed during the gas-phase photo-oxidation of formaldehyde: thermal stability of the HOCH2OO radical
✍ Scribed by F. Zabel; K.A. Sahetchian; C. Chachaty
- Publisher
- Elsevier Science
- Year
- 1987
- Tongue
- English
- Weight
- 398 KB
- Volume
- 134
- Category
- Article
- ISSN
- 0009-2614
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✦ Synopsis
Formaldehyde/oxygen/nitrogen mixtures were photolyzed with UV light in a gas flow system. The reaction mixtures were analyzed by pumping a small fraction of the flowing gas through a microprobe, trapping the condensable compounds on a cold finger (T=96 K), and measuring the ESR spectrum of the solid. The ESR spectra consisted of partly overlapping components from HO1 and HOCHrOO radicals, the latter having g-tensor values g, =2.0025, g,=2.0090 and g,= 2.0320. By simulating the experimental spectra with appropriate amplitude factors for their HO1 and HOCH,OO components, the concentration ratio [HO*] I[ HOCH,OO] was determined. From these values and the H,CO concentrations, measured by UV absorption, equilibrium constants k,, k_ , for the reaction HO2 + H,CO*HOCH,OO were calculated. The expression k,lk_ , = 2.4 x 1 O-26 exp( 15.2 kcal mol-'IRT) cm3 was obtained from measurements in the temperature range 30-100°C.