Detection of Traces of Oxygen in Incandescent Lamps for General Lighting Use

Abstract

To determine traces of oxygen as impurities, existing in conventional incandescent lamps, we investigated the emission of light caused by electric discharges. The total pressure of the gas mixture was 93000 Pa, which consists of approximately 90% of Ar, 10% of N2, and less than 250 ppm of O2. The spectrum decay time of Ar and N2 did not significantly depend on the O2 concentration, while that of O(1S)Ar excimer formed in discharges showed a remarkable dependence; i.e., at the O2 concentration lower than 50 ppm, R (decay constant, [1/sec]) of the excimer was proportional to the O2 concentraiton. The measured decay time well fit the calculation using the Welge and Atkinson equation.5) At O2 concentrations of 50 ppm or higher, R increased with the third power of the concentration. The production of O3 may have accelerated R. Determination of time-dependency of the excimer spectrum enabled determining O2 in conventional incandescent lamps without destroying the envelope.