Afterglow processes responsible for memory effect in nitrogen

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The mechanisms responsible for memory effect in nitrogen at 6.6 mbars have been analysed based on experimental data of electrical breakdown time delay as a function of afterglow period. The analysis has shown that positive ions remaining from previous discharge, as well as metastable and highly vibrationally excited molecules, are responsible for memory effect in the early afterglow. These molecules lead to the formation of positive ions in mutual collisions in the afterglow. Positive ions initiate secondary electron emission from the cathode of a nitrogen-filled tube when voltage higher than static breakdown voltage is applied on the electrodes. On the other hand, N(S4) atoms have a large influence on memory effect in late afterglow. They recombine on the cathode surface forming N2(AΣ3u+) metastable molecules, which release secondary electrons in collision with the cathode. The higher values of electrical breakdown time delay in the case of the tube with borosilicate glass walls than in the case of the tube with copper walls are a consequence of faster de-excitation of neutral active particles on the glass. Indirect confirmation of this assumption has been obtained when the tubes were irradiated with gamma radiation.