Experimental results demonstrate O 2 ( a Δ 1 g ) ( υ = 0 ) formation by catalytic O-atom surface recombination in a room-temperature fused-quartz flow-tube reactor. Resonance-enhanced multiphoton ionization is used to detect O 2 ( a Δ 1 g ) ( υ = 0 ) downstream of a nitrogen discharge flow titrated with nitric oxide to introduce oxygen atoms. A calibration procedure based on ozone photodissociation is developed to quantify O 2 ( a Δ 1 g ) ( υ = 0 ) resonance-enhanced multiphoton ionization signals. Partial pressures of O 2 ( a Δ 1 g ) ( υ = 0 ) in the range of 2.9 to 14 μ torr are measured in the ionization cell for O-atom partial pressures of 1.4–2.9 mtorr atomic oxygen introduced at the titration port. O 2 ( a Δ 1 g ) ( υ = 1 ) could not be detected; an upper limit for the O 2 ( a Δ 1 g ) ( υ = 1 ) partial pressure is one-fifth of the O 2 ( a Δ 1 g ) ( υ = 0 ) partial pressure. A simple chemical kinetics model demonstrates that measured O 2 ( a Δ 1 g ) pressures cannot be explained by gas-phase chemistry alone and must involve O atoms participating in surface reactions. It is found that collisional deactivation of O 2 ( a Δ 1 g ) on the tube walls must be included to satisfactorily model the experimentally observed pressures and trends. Modeling results also suggest that the O 2 ( a Δ 1 g ) surface production yield is 10% or more.


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    Title :

    Singlet Molecular Oxygen Formation by O-Atom Recombination on Fused-Quartz Surfaces


    Contributors:

    Published in:

    Publication date :

    2014-10-08


    Size :

    13 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English




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