Self-absorption-calibrated vacuum ultraviolet absorption spectroscopy for absolute oxygen atomic density measurement

Using a compact microwave plasma light source, a self-absorption-calibrated vacuum ultraviolet absorption spectroscopy (VUVAS) method was developed based on resonance escape factor theory and numerical analysis of the emission profile using Specair . After theoretical calibration of the self-absorption effect for two adjacent oxygen lines at 130.22 nm and 130.49 nm emitted from the light source, absolute oxygen atomic densities were measured for different N 2 /O 2 gas mixture ratios in surface-wave plasmas. The oxygen atomic densities obtained for the two light probes were fairly close, supporting good reliability of the proposed self-absorption-calibrated VUVAS method. It is expected from the present results that the proposed method will extend the range of application of the VUVAS method in industrial plasma processing.