The effect of water vapor on the characteristics of a pulsed-periodic ultraviolet radiation source

Abstract

The effect of a small admixture of water vapor on the optical characteristics of an UV radiation source using a He-air-H₂O mixture as the working medium was studied. The gas mixture was excited in a short-pulse transverse volume discharge operating at a charging voltage of U _ch ≤10 kV. As the partial pressure of helium was varied in the 10–45 kPa range at an air pressure of P(air)=130 Pa and the water vapor pressure within P(H₂O)=50–100 Pa, the main optical emission from plasma in the UV wavelength range was concentrated in a broad band peaked at λ_max=309.7 nm and was two times greater than the intensity of the base emission bands of the nitrogen molecule in this spectral range (λ=337.1 and 315.9 nm, N₂(C-B)). Adding water vapor to the He-air mixture increases the spectral range of the UV source toward shortwave region, which is related to a spontaneous decay of the products of dissociation of water molecules.