Voltage–current characteristics of low-pressure discharges in vapors of several alcohols

In this paper, we present the results for voltage–current (V–i) characteristics of dc low-pressure low to moderate current discharges in vapors of alcohols: methanol, ethanol, isopropanol, and n-butanol vapors. These electrical measurements are supported by optical recordings of axial emission profiles from low-current to high-current regimes. The voltage–current characteristics and the corresponding distribution of emission intensities were typically recorded for two pd values, in the left-hand branch of the Paschen curve (0.15 Torr cm) and in the minimum of the Paschen curves (ranging from 0.30 to 0.40 Torr cm for different alcohols selected here). In the recorded V–i characteristics, the different discharge regimes of discharge operation are easily distinguished. Axial profiles of emitted light from the low-current to high-current regimes reveal that heavy particles make up a significant contribution to excitation part in alcohol vapor discharges. In the region of transition from normal to abnormal glow in the methanol vapor discharge, sudden changes of the regime of operation were observed and several diagnostic techniques have been applied to them.