O 2 ( Δ 1 ) production in He∕O2 mixtures in flowing low pressure plasmas

Chemical oxygen-iodine lasers (COIL) are attractive for diverse industrial applications because they are capable of high efficiency, high power operation, and because the 1.315 mm wavelength can be transmitted through fiber optics and couples efficiently with most metals. Conventional COILs are pumped with O2s1Dd that is generated by reaction of Cl2 in a basic H2O2 solution. Current trends in pumping COILs involve producing the O2s1Dd in electric discharges, thereby circumventing the hazards, complexity, and weight associated with pumping and storing caustic liquids. In this work, we have investigated the scaling of O2s1Dd yields with specific energy deposition in He/O2 mixtures in flowing radio frequency (rf) discharges at pressures of a few to tens of Torr using a global plasma kinetics model. We found that O2s1Dd yield increases nearly linearly with specific energy deposition in O2 molecules up to a few eV per molecule, with yields peaking around 30 % by 5–8 eV. Further increases in specific energy deposition serve only to increase O2 dissociation and gas heating, thereby reducing the O2s1Dd yield. We also found that variations in peak yields at a given specific energy deposition are caused by secondary effects resulting from dilution, pressure, and power level. We show that these secondary effects alter the O2s1Dd yield by shifting the O2s1Sd /O2s1Dd ratio. © 2004 American Institute of Physics. [DOI: 10.1063/1.1768615] I