Isotopes of water molecules in a glow discharge in mixtures of helium with H2O and D2

The article presents the results of theoretical and experimental research on the concentrations of water isotopomers (H2O, HDO, and D2O) in plasma of a DC discharge in mixtures consisting of helium, molecular deuterium, and water vapor. Dependence of the isotopomers concentrations on the initial mixture composition is described. The measurements were performed using tunable diode laser absorption spectroscopy (TDLAS). Theoretical results were obtained with the use of a homogeneous kinetic model. The model included the balance equations for charged and neutral particles and the Boltzmann equation for the electron energy distribution function in the two-term approximation. The experimental and theoretical values of H2O and HDO concentrations were compared and showed good agreement.