Chemiluminescent Phenomena during Hydrocarbon Combustion

Abstract

THE light emission accompanying the combustion of hydrocarbons in explosions and high-temperature flames has received a great deal of attention and it seems generally agreed that, while normal thermal radiation is present, part of the radiation is non-thermal in origin. Most of the studies have been concerned with radiation which is an integration of light emission over a period of time during which many different stages of reaction and excitation may occur. By means of flash photolysis, we have described how homogeneous initiation of explosions may be brought about and relative radical concentrations measured as a function of time throughout the reaction^1,2. In order to investigate reversal temperatures and the problem of chemiluminescence, we have now extended our work to the kinetic recording of emission and absorption spectra by photo-electric methods. For this purpose, the spectrograph plate-holder was replaced by a mounting carrying photomultiplier cells behind adjustable slits. The photocell outputs were fed through D.C. amplifiers on to an oscillograph, the overall response-time being about 10⁻⁶ sec. For absorption measurements the light from a xenon arc was focused first in the centre of the reaction vessel and then on to the spectrograph slit by means of quartz lenses. In these ways it was possible to record very rapid changes in the emission or absorption of selected spectral regions. This has revealed several remarkable features which were not apparent in the earlier work and which have an important bearing on the problem of radiation from combustion processes.