Spectroscopic study of a surface-wave-sustained argon plasma column at atmospheric pressure by means of a power interruption technique

The instantaneous response and the temporal evolution of the intensity of some atomic lines to the sudden interruption of the high frequency (HF) power maintaining the discharge have been studied in an argon microwave-induced plasma (MIP) sustained by a surface wave at atmospheric pressure. The instantaneous response permits the detection of possible departures from the Local Thermodynamic Equilibrium (LTE) existing in the steady-state discharge and confirms that these discharges behave as a two-temperature plasma, in the investigated conditions. Furthermore, this response has allowed the determination of the elementary balances controlling the excited level populations. In turn, the so-called temporal evolution of the line intensities has given additional information about the processes governing the electron losses during the extinction in this type of discharge.