Emission from a DC glow discharge in a He/H2O mixture

The electrical and optical characteristics of a longitudinal dc glow discharge in a cylindrical discharge tube in mixtures of helium with saturated water vapor at room temperature are investigated. In the UV range, a broad band with a maximum at λ_max=309.6 nm and Δλ=9 nm prevails. The H_α 656.3-nm, H_β 486.1-nm, and HeI lines in the range 440–670 nm are the main diagnostic spectral lines. The helium partial pressure and the glow discharge current are optimized to achieve the maximum intensities of the 309.6-nm band and HeI and HI spectral lines. The results obtained are of interest for the development of an ecologically safe radiation source based on the products of the decomposition of water molecules and clusters in plasma.