Abstract
Low-pressure air micro-plasmajets with a length of 10mm were generated through a nozzle with a diameter of 0.7mm at the pressures of 31.3 and 5.3kPa. Spectroscopic measurements were conducted at the point of 0.5mm from the nozzle exit on the central axis. The N2+ 1- and N2 2+ bands were predominant in the wavelength region of 280 to 420nm and the band shape was almost independent of the pressure. From temperature determination by a spectral matching method, it was found that the plasmajets were in a thermal nonequilibrium state and that vibrational temperature was much higher than rotational one. The experimental intensity distribution was reconstructed by the equilibrium radiation theory, in good agreement except for the N2 2+ bands with v′ ≥ 2 as in case of atmospheric air micro-plasmajet. For these bands, much better agreement was obtained by taking the effects of predissociation and non-Boltzmann rotational population distribution for N2C3Πu state into consideration in the theory. Discussions were made about potential cause of high vibrational temperature and slight difference between experimental and theoretical band shapes of the N2 2+ bands at the low-pressures.
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