Butane-flame, core/sheath spectra

Spectra from two parts of a butane gas flame (air-mixed - top; unmixed gas - bottom). Compared with the candle flame, the near infrared contains much stronger emission bands of water. The deep blue colour of the flame sheath is due to the recombination of free electrons with positive ions. The strong emissions from the visible (blue-green) part of the flame are due mostly to the C_2 molecule (two carbon atoms) but also to CN and CH.

The orange line shows a black body (Planck) spectrum which corresponds to the brightest, white-yellow, part of a candle flame - similar to the yellow tip of the bottom image. The broad, light-orange band is the infrared camera bandpass.

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