Schematic figure showing the low-temperature ( ≤ 250 K) dielectronic recombination of N ii through the fine-structure autoionizing levels between the two lowest ionization thresholds of N iii ²P° _1/2 and ²P° _3/2. The electrons captured to the high-n autoionizing levels decay to low-n bound states through cascades and optical recombination lines (ORLs) are thus emitted. Here Multiplets V3, V19 and V39 are presented as examples.