Improved RF plasma jet generation of singlet delta oxygen

RF oxygen plasma jets were studied experimentally as an alternative source of molecular singlet delta oxygen for an oxygen-iodine laser. The relative yield of singlet delta oxygen was measured under a wide variety of experimental conditions. The RF frequency range was 27.2-99.9 MHz and the RF power was up to 200 W. The oxygen output pressure was 0.05-0.40 Torr and the oxygen flow rate was 195-1000 seem. High purity oxygen or its mixtures with Ar, N-2, NO and Hg at the pumping velocity of 250 m(3)/h were used. The plasma jet was produced in nozzles, having the inner diameter of 1-6 mm and the length of 1-16 mm. The nozzle materials Al, Ti, Ta and W gave significantly better results than Pt and Ni. The dependence of singlet delta oxygen production on the radiofrequency was increasing monotonously. Other dependencies were not monotonous and exhibited an optimum. The cw mode of operation gave usually better results than a pulsed mode. The most effective admixture was N-2, which gave the highest enhancement. This resulted in the relative yield of singlet delta oxygen exceeding 15%.