Optical Emission Spectroscopy of a Pulsed Electrical Discharge in Gas Bubbles in Water

Abstract

Summary form given only. Pulsed electrical discharges in water have been investigated for water decontamination and decoloration. The optimization of the cleaning process requires detailed knowledge of the discharge process, particularly in terms of the formation of active species such as OH, O, and other radicals. Rectangular voltage pulses of 1 mus duration are applied to single Ar or oxygen bubbles in water and optical emissions from the discharge are studied as a function of applied voltage, power delivered to the discharge, and the total energy supplied or the number of pulses applied to each bubble. Average and time-resolved spectra have been recorded from Ar and oxygen bubbles in various spectral ranges from 285 nm to 880 nm. We observed increases in emission intensity with power for OH and other emissions confirming that the radical formation increases with increasing power. Ar lines and OH vibrational bands were used to determine the electron, vibrational, and rotational temperature in the discharge. Spectra were taken in 200 ns time windows during a single pulse and additional time-resolved information has been obtained using a fast photomultiplier tube with band-pass filters. This information allows us to speculate on the dynamics of the radical production and other processes in the pulsed discharge.