Optical emission spectroscopy of the active species in nitrogen plasma

Optical emission spectroscopy is used to study the production of active species in nitrogen plasma excited by a 50 Hz pulsed-dc power source. The emission intensities of the band heads of the second positive (lambda = 337.1 nm; 0-0) and first negative (lambda = 391.4 nm; 0-0) systems are used to investigate the dependence of their radiative states N-2 (C-3 Pi(u)) and N-2(+)(B-2 Sigma(+)(u)) population density on operating parameters. The emission intensity of the N-2(+)(B-2 Sigma(+)(u)) radiative state is used to determine the relative dependence of N-2(+) ion density on operating conditions by considering the fact that, in low-temperature plasmas, the dominant mechanism of the population of N-2(+)(B-2 Sigma(+)(u)) state starts from the ground state N-2(+)(X-2 Sigma(+)(g)) mainly by electron collisions. It is found that the production of these active species has a significant dependence on the discharge parameters and may be optimized under typical operating conditions.