Absorption spectroscopy of flames

• Main Author: Jessen, Peter Friedrich
• Published: Imperial College London 1968
• Subjects: 535
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.623057

Absorption spectra of the radicals C2, C3 and CH have been studied quantitatively in acetylene-oxygen flames burning at atmospheric pressure. The effective light path through the flame was increased by using a new design of multiple reflection system. This focuses the light into the flame, gives better spatial resolution and is less affected by schlieren-type deflections of the light beam 0 than in the normal parallel-beam system. There is little evidence for thermal disequilibrium in the luminous mantle of fuel-rich flames. Concentrations of C2 and C3, about 2x1014 and 1x1015 molecules cm-3, are consistent with values calculated for equilibrium with solid carbon, but the concentrations of C2 and CH are much higher in the reaction zone. Measurements of C2 rotational and vibrational temperature support a chemiluminescent mechanism of formation. It is concluded that C3 is formed from evaporation of incipient carbon particles but the possibility of C2 radicals being important in the formation of carbon 'nuclei' cannot be ruled out.