The memory effect, due to postafterglow survival of some species which affect subsequent breakdown, was analyzed from the behavior of memory curves. In early afterglow, up to several tens of a millisecond, the memory effect in nitrogen is a consequence of the presence of positive ions formed by the collision between metastable molecules and highly vibrationally excited molecules remaining from the previous discharge. In late afterglow, the memory effect is due to $\mathrm{N}{(}^4\mathrm{S)}$ atoms created during the previous discharge and in early afterglow. When the atom density is reduced enough the breakdown is initiated by cosmic rays which always exists. In late afterglow in nitrogen the memory effect is very sensitive on cathode material.

The processes which are a consequence of neutral active particles presence in post-discharge nitrogen-filled tube at 13.3 mbar pressure have been analyzed. The analysis has been performed based on the experimental data of electrical breakdown time delay as a function of afterglow period $\tau .$ The most significant parameters such as applied voltage, discharge current, time, and exposure to radiation have been varied. It has been shown that the increase in applied voltage and discharge time, as well as exposure to UV radiation, leads to the decrease of the mean value of electrical breakdown time delay ${\overline{t}}_d.$ This decrease occurs for $\tau >70\hspace{0.17em}\text{ms},$ when $N({}^4\mathrm{\text{S}})$ atoms play a dominant role in breakdown initiation. The increase in discharge current leads to the decrease of ${\overline{t}}_d$ values for $\tau \le 70\hspace{0.17em}\text{ms},$ when positive ions dominantly induce breakdown. The most important reactions which lead to formation of positive ions and neutral active particles are also presented in the paper.

Memory effect in nitrogen based on experimental data of electrical breakdown time delay as a function of afterglow period in the presence of additional electrons has been investigated. The additional electrons were supplied as a result of extraction from the auxiliary electrode pair or nitrogen irradiation with the radioactive sourceof low activity. The results show that these electrons have an important role in the recombination of positive ions formed in mutual metastable molecules' collisions and collisions between metastable and highly vibrationally excited molecules in the early afterglow. As a consequence of the ion–electron recombination N(⁴S) atoms are formed which, as well as N(⁴S) atoms formed in previous discharge, have a significant influence on the memory effect in late afterglow. The presence of N(⁴S) atoms in the late afterglow is tracked by monitoring the secondary emission which they induce via catalytic recombination on the cathode of a nitrogen-filled tube. Also, it has been shown that the contribution of secondary electrons which originate from N(⁴S) atoms and Compton electrons when the radioactive source is and isn't present can be distinguished.