Description and Analysis of a Vacuum Ultraviolet Atomic Line Source

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Abstract
An intense vacuum uv atomic line source excited in a 2450-MHz microwave discharge cavity is described and analyzed. Additional features are a clean spectrum, very little window deterioration, little or no self-absorption, and easily interchangeable parts. (For the O-atom source only the 1300-Å triplet shows up over the 1200-Å to 1650-Å region.) This source is suitable for the detection of various species by absorption measurement in fast occurring events such as those in ballistic ranges and shock tubes. Atomic line shape theory is used to analyze an O-atom line source with intensity ratios I1306Å:I1305Å:I1302Å:1:2.9:4.5. This source is described by a 2700 ± 200 K temperature and certain self-absorption parameters as deduced from the measurement of their intensity ratios and their transmission characteristics through known concentrations of O-atoms. A good theoretical fit to the measured transmission validates the assumed uniform source temperature and excitation for the analysis. An f value (f = 0.052 ± 0.005) for the O-atom 1300-Å triplet absorption and a collision diameter of 5.5 ± 1.0 Å between the O-atom and the nitrogen molecule were determined in the course of this study.