Free radical and atom activity at a pyrex glass surface as a source of sodium D line emissions during combustion reactions
✍ Scribed by D.L. Baulch; J.F. Griffiths; R. Richter
- Publisher
- Elsevier Science
- Year
- 1991
- Tongue
- English
- Weight
- 246 KB
- Volume
- 85
- Category
- Article
- ISSN
- 0010-2180
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✦ Synopsis
Hydrogen plus oxygen mixtures are able to undergo oscillatory ignition in a stirred-flow reactor . The temperature approaches that of the adiabatic flame during each oscillation and high free radical and atom concentrations are attained . We have measured hydroxyl radical concentrations of 10 -8 mol cm -3. The oscillatory ignition originates in a kinetic interaction between chain branching and chain termination processes, with supplementary effects of the accompanying heat release. The investigation and interpretation of the oscillatory reaction has been reported in detail elsewhere [1-5], A visible light emission also pervades the gaseous volume during ignition that corresponds to the frequencies of the sodium D lines. The emission originates from sodium atoms that are released from the Pyrex glass of the reaction vessel surface. (Similar effects are observed when Pyrex glass is held in a Bunsen burner flame.) We report experimental results obtained by emission spectroscopy that link the release of the sodium atoms and their associated emission to reactions at the vessel surface involving the atoms or free radicals formed during ignition.
Experimental details of the stirred-flow experiments have been described previously . Here we summarize only the main features. Experiments were carried out in a cylindrical, Pyrex glass, jet-stirred reactor (0.5 dm 3) located in a recirculating-air oven. The vessel was maintained at constant temperature (___0.5 K) for a considerable period. Reactant flow rates of hydrogen and oxygen in fixed proportions and at constant pres-