Kinetics of the Electrical Discharge Pumped Oxygen-iodine Laser

A systematic study of microwave discharges at 2.45 GHz has been performed through the pressure range of sustainable electric discharges in pure oxygen flows of 2 to 10 Torr. A corresponding study of 13.56 MHz has also been performed at pressures of 2, 4, and 7 Torr. Optical emissions from O2(a 1Δ), O2(b 1Σ), and O-atoms have been measured from the center of a μ-wave discharge. Discharge residence times from 0.1 to 5 ms have been reported. The O2(b 1Σ) emissions, with a spectral resolution of 0.01 nm, have been used to measure the temperature of the gas, which typically reaches a steady-state of 1,200 K. The interpretation of the measured O2(a 1Δ), yield, using a streamlined, nearly analytic model, cast new light on the kinetics within the electric discharge. The pseudo-first order quenching rate of O2(a 1Δ) ranges from 6,000 s-1 for μ-wave discharges to 600 s-1 for radio frequency (RF) discharges, independent of gas pressure and flow rate. The observations are consistent with a second order reaction channel that is dependent on both the electron and oxygen ground state concentrations. The role of vibrationally excited ground state oxygen is explored and provides a plausible destruction mechanism.