Identification of the emitters of some visible alkaline-earth bands in flames

A method is described to identify the emitters (monoxide or hydroxide) of some visible alkaline-earth bands in flames. This method is based on the measurement of the ratio of band to atomic line intensity for a given element in two flames of the same temperature but with a different, known gas composition. In this paper, this method is applied to C₂H₂-air, H₂-air and moist CO-N₂-O₂ and CO-nitrous oxide flames. It appears that in all of these flames the calcium bands found at 5540, 6020 and 6230 Å, and the strontium bands at 6060, 6470, 6690 and 6820 Å are definitely due to the monohydroxide, whereas in the C₂H₂-air flame the barium bands found at 4870 and 5120 Å are due to both oxide and monohydroxide.