Abstract:
The results of studying a capacitive discharge in water vapor are reported. This discharge is an effective and environmentally friendly source of UV radiation due to hydroxyl OH ($A^2\Sigma^+\to X^2\Pi$ transition) in the wavelength range 280–330 nm. It is shown that, at $E/N <$ 210 Td, the discharge is greatly influenced by dissociative attachment of electrons, while at $E/N >$ 210 Td, ionization dominates over dissociation. The formation rate of excited OH* radicals $(A^2\Sigma^+)$ in the water-vapor discharge is much higher than the formation rate of emitting states in hydrogen and oxygen atoms. As $E/N$ grows, the ratio between the intensities of OH lines and atomic hydrogen Balmer series decreases. According to estimates, $E/N$ values optimal for the OH radical line excitation fall into the range 250–400 Td.
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