Inhomogeneous microwave discharge in oxygen

Results are given of one-dimensional quasi-static simulation of steady microwave discharge in a system of electrodes with spherical symmetry in oxygen at pressures of $1$ to $8$ torr. The model includes the equation for electric field intensity in quasi-static approximation, Poisson equation, balance equations defining the kinetics of charged and neutral particles of plasma, and steady-state homogeneous Boltzmann equation for electrons. The well-known analytical expression for vibrational distribution of molecules, derived in diffusion approximation, is used for including the processes which involve vibrationally excited particles. It is demonstrated that the presence of negative ions does not result in differences of the electrodynamics of discharge from those of discharge in nitrogen. The composition of heavy component of plasma is investigated and, in particular, it is demonstrated that the concentration of molecules in the $\text{O}_2$ ($a^1\Delta$) state may be as high as $20$ $\%$.