Spectroscopic measurements of microwave-discharged low-pressure nitrogen plasmas were made in a tube with a diameter of 9.5 mm and length of 42 mm. Intense radiation of N 2 2+ bands and weak radiations of N 2 + 1−, N2 1+, and NO γ bands were observed. Unique intensity distribution of N2 2+ bands with high vibrational levels was observed as in the arc-discharged micro-air plasma-jets. Rotational and vibrational temperatures were determined by a spectral matching method with N 2 2+ (0, 2) and (1,

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... 3) bands. The vibrational state of the plasma was also investigated by the N 2 2+ band intensity. As the experimental spectra could not be reconstructed by a usual equilibrium radiation theory with one rotational temperature, the theoretical spectra were constructed with the effects of predissociation and theoretical non-Boltzmann rotational population distribution, and were compared with the experimental ones. As a result, it was found that the vibrational and rotational temperatures were dependent on the theoretical model for rotational population distribution, that the rotational temperature was dependent on the vibrational states, and that the plasmas were in the vibrational non-equilibrium state.