Mode transition in radio-frequency atmospheric argon discharges with and without dielectric barriers

In this letter, basic characteristics of glow modes and their mode transition are studied for radio-frequency (rf) atmospheric argon discharges with bare and dielectrically insulated electrodes. Through input power control, large-volume rf atmospheric argon discharges with bare electrodes are achieved in the α mode via an abrupt transition from a constricted γ mode, whereas dielectrically insulated electrodes result in large argon discharges in both the α and γ modes with gradual mode transition. Current dependence of the 750 nm line intensity and of the gas temperature are shown to capture clearly the signature of mode transition.