Swan band
![Spectrum of the blue flame from a butane torch showing excited molecular radical band emission and Swan bands.](/Images/godic/202502/14/Spectrum_of_blue_flame5231.png")
Swan bands are a characteristic of the spectra of carbon stars, comets and of burning hydrocarbon fuels. They are named for the Scottish physicist William Swan who first studied the spectral analysis of radical Diatomic carbon C2 in 1856.
Swan bands consist of several sequences of vibrational bands scattered throughout the visible spectrum.