Species kinetics in Ar-S₂ plasma of the pulsed periodic discharge

The kinetic (0D) model a longitudinal pulsed-periodic discharge in mixtures of sulfur vapor with argon based on solution of the balance equations for plasma species and an equation of the electron energy balance was developed and evolution of species densities was calculated in the discharge at pressure ∼ 40 Torr. Radiation spectrum of the discharge is similar to solar spectrum in the wavelength range of 280–600 nm. The discharge plasma is electronegative; a discharge with electropositive plasma is non-stable and can exist during short time in a pulsed mode. As simulation shown densities of all charged and excited species fast increase during 1–1.5 μs after voltage pulse beginning, reach maximal values and then decrease because of diminishing electrons mean energy and density in decreasing field. It is found that density of S₂ ^*(B ³Σ) molecules fast rises during voltage pulse and exceeds densities of other excited species; however when a pulse voltage decreases the density of S₂ ^*(B ³Σ) molecules fast falls while density of resonance excited argon atoms decreases slower. This is the reason for appearance of strong Ar lines together with S₂ bands in spectra of the longitudinal pulsed-periodic discharge in argon/sulfur vapor mixtures. (paper)