[The optical characteristics of hollow cathode discharge striations in nitrogen]

The characteristics of striations in cylindrical hollow cathode discharge were investigated experimentally. The spectra of striations were measured at a pressure of 20 Pa in a discharge of 1.3 mA, in which the main spectra are the emission spectrum lines of the N2 first positive band (B3pi(g)-->A3pi(u)) and second positive band system (C3pi(u)-->B3pi(g)). The spatial characteristics of vibrational temperature of N2 were calculated based on the theory of double molecular spectrum. It is shown that the emission intensity exhibits a periodic structure with an unequal magnitude, and the spectral intensity of bright striation is higher than that of dark striations. The vibrational temperature of bright striation is of the value of 3500-4400K, moreover the vibrational temperature in the bright regions decreases from the cathode to the anode. In addition, the characteristics of striations at 1.0 mA and 1.5 mA were obtained, and the influence of discharge current on the striations was investigated. It is shown that the vibrational temperature and the distance between two striations increase. Finally the reduced electric field was calculated, which is about 44 approximately 49 m(-1) x Pa(-1), moreover it decreases with the increase in discharge current. The results are very useful for understanding the mechanism of discharge striations and for improving the stability of hollow cathode discharge.