CN* band spectrum in spark emission spectroscopy

An arc between carbon electrodes in air has enough energy to activate the nitrogen in the air. The nitrogen then behaves as nitrogen in the combining form and by reaction with the carbon from the electrodes, the CN bands are produced. To prevent this, special arrangements, such as using an inert gas to remove adsorbed nitrogen from the surface of the electrodes, have to be made.


In our experiment, no particular precautions were made, and nevertheless CN bands were not found.


Why?


