Additional studies of rf plasmoids

Data have been obtained that support the belief that the particular form of the static-electric-potential profile that arises when negative ions are present in an rf plasmoidal discharge is necessary for the formation of dark-sheath plasmoids. In addition, ethanol and acetone vapors have been found to yield visible emission spectra containing the prominent lines of the CO+ comet tail system which readily reveal dark-sheath plasmoid characteristics. Pure water-vapor discharges do not exhibit dark-sheath plasmoids, but in the presence of air impurities the conditions necessary for the formation of a dark sheath apparently arise when the relative intensity of the O2+ spectrum is large enough.