Characterization of nitrogen glow discharge plasma via optical emission spectrum simulation

Optical emission spectroscopy in nitrogen glow discharge plasma is simulated, and the collision excitations and characteristic emissions of the species (N-2, N-2(+), N+, N) are investigated by a Monte Carlo model for nitrogen molecular gas discharge. The excitation rates of the main excited states are calculated and the corresponding relation and relative magnitude between the distribution of excitation rate of a certain excited state and the distributions of the emission rates of various lines originating from this excited level are also explored. The simulated results are compared with the experimental measurements in two typical discharge conditions. The luminescence mechanism of the line N-2(+) : 391.4 nm is explained based on the microscopic plasma processes. The cathode glow in N-2 discharge is found to be mainly caused by N+ impact excitation and the intensity of cathode glow decreases with the voltage. The corresponding relation between the emission rate or intensity of the 391.4 nm line and the production rate and the density of N-2(+) is also examined.