Microwave Study of Afterglow Discharge in Water Vapor

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Abstract
Results of a microwave investigation of decaying plasmas produced in water vapor H2O are reported. Electron loss processes prevailing in these decaying water vapor plasmas were interpreted. In the electron density range from 1010 to 108 per cm3, electron‐ion recombination prevails as the dominant electron loss process with a coefficient of 10−6 to 10−5 cm3/sec. For vapor pressures up to 7.0 mm Hg, electron attachment to water vapor molecules or their derivatives was too small to be detectable, i.e., an attachment probability less than 10−7. The electron collision probability for momentum transfer collisions with water vapor molecules was measured to be 2300±500 cm−1 mm Hg−1 for electrons near thermal energies at room temperature. The collision probability steeply decreases with increasing electron energy in the low energy range. An interpretation of the de‐ionization processes in TR tubes filled with admixtures of water vapor and noble gases is given.