Excitation of molecules in the afterglow of an electric discharge

The afterglow of an electrical discharge under reduced pressures (1-10 torr) of nitrogen, argon, helium or a mixture of two of these is used to examine the excitation process for atomic and molecular species. Emissions of benzene and anthracene are not observed in any of the systems. The metastable species, N ₂ (A), is shown to be responsible for excitation of mercury and nitric oxide.