Studies of the explosive combustion of hydrocarbons by kinetic spectroscopy - II. Comparative investigations of hydrocarbons and a study of the continuous absorption spectra

Abstract

The absorption spectra of explosions of ethylene, ethane and methane with oxygen, initiated by the flash photolysis of nitrogen dioxide, have been studied kinetically by flash spectroscopy and the results are compared with those already given for acetylene. The occurrence of the diatomic radical spectra is qualitatively similar in the four hydrocarbons, but there are important quantitative differences in the stoicheiometry of the mixtures which give equivalent spectroscopic results. The continuous spectra and the spectrum of C 3 have been studied in more detail. The continuum which is present after the explosion is shown to be due to absorption by carbon particles. A second intense continuous spectrum, which has a characteristic maximum at 3900 Å and whose occurrence follows closely that of the radicals C 2 and C 3 , is attributed to a carbon molecule which is in approximate thermal equilibrium and whose concentration must form a considerable fraction of the total carbon present in the vapour during the explosion.