Density of metastable atoms in an argon plasma produced by an RF surface wave

The maximum density of argon atoms in excited metastable states, in a plasma produced by surface wave propagation, is studied experimentally. Measurements are performed by the absorption method, perpendicularly to the tube axis. The measurements show that the maximum population densities of the 3p 5 4s metastable levels in argon are larger in the RF plasma than in the positive column of a glow discharge, between 0.02 and 0.4 Torr in a 26 mm i.d. tube. This fact could be used to improve gas laser operation.