Observation of Self Absorption of Mercury I and Cadmium I Emission in an Atmospheric Microwave Sustained Plasma
摘要:
Atomic emission spectroscopy of a continuous, atmospheric-pressure microwave sustained plasma in an undiluted slip stream of stack exhaust is under development for real-time monitoring of EPA-regulated hazardous metals (As, Be, Cd, Cr, Hg, and Pb). The detection limit in such a plasma for two of these metals at their strongest transitions, Cd I 228.8nm and Hg I 253.65nm, has been found to depend on the path length between the plasma and the detection system. Measurements were carried out on long plasma columns (>100mm ×10mm diameter) sustained in air by approximately 1.5kW power at 2.45GHz. The detection limits, using a long path-length axial view for UV light collection versus short path-length side views at different points along the plasma column, have shown a clear diminution of the signal for the axial view. Self-absorption by unexcited atomic cadmium and mercury is shown to be responsible for diminution of the axial signal. The Cd I 228.8nm transition was observed to reverse from an emission feature to an absorption feature when the axial path-length for the light was extended.
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DOI:
10.1039/A908075I
被引量:
年份:
1999

























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